18 Jan, 2023

Open Redirect Vulnerability

Vulnerability Assessment as a Service (VAaaS)

Tests systems and applications for vulnerabilities to address weaknesses.

The abbreviation for an Open Redirection vulnerability is “URL Redirection” or “Open Redirect” vulnerability.

An open redirect vulnerability is a type of security vulnerability that occurs when an application or website redirects a user to an arbitrary, external URL. This can happen when the application or website uses user-supplied data in the redirection process, such as a URL parameter, without properly validating or sanitizing the input. This can allow an attacker to craft a malicious link that redirects a victim to a malicious website or phishing page, potentially stealing sensitive information or spreading malware. It is also known as “unvalidated redirects and forwards” vulnerability.

An example of an open redirect vulnerability would be a login page that redirects a user to the URL specified in a “return” parameter after a successful login. If the application does not properly validate the “return” parameter, an attacker could craft a link with a malicious URL in the “return” parameter, tricking the user into being redirected to a malicious website after logging in.

Open redirect vulnerabilities can be mitigated by properly validating and sanitizing user-supplied data in the redirection process, and by only allowing redirects to trusted and approved URLs.

Example of vulnerable code on different programming languages:

In PHP:

				
					$redirect_url = $_GET['redirect_url'];

header("Location: ".$redirect_url);
				
			

 

In this example, the PHP script takes the “redirect_url” parameter from the GET request and uses it to set the location header. If the application does not properly validate the “redirect_url” parameter, an attacker could craft a link with a malicious URL in the “redirect_url” parameter, tricking the user into being redirected to a malicious website.

In ASP.NET

				
					string redirectUrl = Request.QueryString["redirectUrl"];

Response.Redirect(redirectUrl);
				
			

In this example, the ASP.NET script takes the “redirectUrl” parameter from the query string and uses it to redirect the user. If the application does not properly validate the “redirectUrl” parameter, an attacker could craft a link with a malicious URL in the “redirectUrl” parameter, tricking the user into being redirected to a malicious website.

In Java

				
					String redirectUrl = request.getParameter("redirectUrl");

response.sendRedirect(redirectUrl);
				
			

This Java code takes the “redirectUrl” parameter from the request and uses it to redirect the user. If the application does not properly validate the “redirectUrl” parameter, an attacker could craft a link with a malicious URL in the “redirectUrl” parameter, tricking the user into being redirected to a malicious website.

It’s important to note that these examples are just a demonstration of open redirect vulnerability and should not be used in production as they are vulnerable to the attack.

Examples of exploitation Open redirect vulnerability.

Open redirect vulnerability would be a website that redirects users to a specified URL without properly validating it. For example, imagine a website has a login page that redirects users to the homepage after they log in. The website’s code might look something like this:

				
					http://example.com/login?redirect=http://example.com/home
				
			

The problem with this is that an attacker could potentially redirect users to a malicious website by manipulating the “redirect” parameter. They might send the following link to a victim:

				
					http://example.com/login?redirect=http://attacker.com
				
			

When the victim clicks on the link, they would be redirected to the attacker’s website instead of the legitimate homepage. This could be used to phish for sensitive information or to deliver malware.

It is important to note that this is just one example of open redirect vulnerability and other vectors exist. It is also important to validate the redirect URL and not to trust any input from user or any other external source.

Privilege escalation techniques.

There are many techniques that can be used for privilege escalation, but the specific technique will depend on the vulnerability and the system that is affected. Here are a few examples of privilege escalation techniques that could potentially be used:

  1. Exploiting a software vulnerability: An attacker could exploit a software vulnerability, such as a buffer overflow, in order to gain elevated privileges on the affected system.

  2. Abusing misconfigured permissions: An attacker could take advantage of misconfigured permissions on a system in order to gain access to resources that they would not normally have access to.

  3. Pass the hash: An attacker could use a pass the hash attack to authenticate to a system using the hash of a valid user’s password rather than the password itself.

  4. Exploiting a service: An attacker could use a vulnerability in a service or daemon running on a system in order to gain elevated privileges.

  5. Using a privilege escalation exploit: An attacker could use a privilege escalation exploit that is specific to the operating system or software that is running on the system.

  6. Exploiting a kernel vulnerability: An attacker could exploit a vulnerability in the kernel of the operating system in order to gain elevated privileges.

It is important to note that not all the techniques are applicable to all the systems and it depends on the scenario. Also, it is important to always keep the systems up to date and have a proper access control policy in place.

General methodology and checklist for testing for open redirect vulnerabilities

Methodology:

  1. Identify all potential redirect locations on the application, such as login pages, logout pages, 404 pages, and any other pages that may redirect the user to another location.

  2. Test each redirect location for vulnerability by injecting various payloads, such as “http://attacker.com“, “javascript:alert(1)”, “data:text/html;base64”, “file:///etc/passwd” etc, into the redirect parameter.

  3. Examine the application’s response to each payload to determine if the redirect location is vulnerable.

  4. If a vulnerability is identified, attempt to exploit it by redirecting the user to a malicious website or injecting malicious code into the application.

  5. Document all findings and provide recommendations for remediation.

Checklist:

  • Identify all potential redirect locations on the application

  • Test each redirect location for vulnerability by injecting various payloads

  • Examine the application’s response to each payload

  • Attempt to exploit the vulnerability

  • Document all findings and provide recommendations for remediation

It is important to note that this is a general methodology and checklist and it can be adjusted and improved based on the specific scenario. Additionally, it is important to always conduct a thorough testing and not to rely on automated tools alone. Also it is important to follow the laws and regulations of the country you are conducting the testing on.

Tools set for exploiting open redirect vulnerabilities

There are several software tools that can be used to test for open redirect vulnerabilities and to automate the process of identifying and exploiting these vulnerabilities.

Here are a few examples:

1. Burp Suite
2. OWASP ZAP
3. NMap
4. Wfuzz
5. sqlmap
6. Vega
7. Acunetix
8. Arachni
9. Nikto
10. OpenVAS
11. Nessus
12. Fiddler
13. Telerik Fiddler
14. Charles
15. Paros
16. WebScarab
17. Skipfish
18. Wireshark
19. Metasploit
20. OWASP DirBuster
21. OWASP W3AF
22. OWASP Wapiti
23. OWASP Arachni
24. OWASP JoomScan
25. OWASP Skipfish
26. OWASP XSSer
27. OWASP A2SV
28. OWASP ZED Attack Proxy
29. OWASP AppSensor
30. OWASP IronWASP
31. OWASP WebGoat
32. OWASP WebSlayer
33. OWASP WebScarabNG
34. OWASP WebSecurityTestingFramework
35. OWASP WebSecurify
36. OWASP WebCruiser
37. OWASP Clickjacking Tester
38. OWASP XSS Me
39. OWASP XSS Filter Evasion Cheat Sheet

For manual testing of open redirect vulnerabilities typically involve manually identifying potential redirect locations, such as login pages, logout pages, 404 pages, and any other pages that may redirect the user to another location, and then testing each redirect location by injecting various payloads and examining the application’s response.

It’s important to note that manual testing is not a tool per se, and it’s a methodology or a process that involves using various techniques and methodologies to identify the vulnerabilities. Tools like Burp Suite, OWASP ZAP, and WebScarab, etc. can assist and facilitate the manual testing process by providing a proxy, an intercepting proxy, and a web application scanner that can be used to test for open redirect vulnerabilities.

Manual testing including:

  1. Identify all potential redirect locations on the application

  2. Test each redirect location for vulnerability by injecting various payloads

  3. Examine the application’s response to each payload

  4. Attempt to exploit the vulnerability if found

  5. Document all findings and provide recommendations for remediation

It’s important to note that this list is not exhaustive and there are many other tools available as well, also some of these tools may have other functionalities besides open redirect testing and they can be used as part of a comprehensive security testing process. Additionally, it’s important to remember that automated tools are not a substitute for manual testing, and you should always conduct a thorough manual testing as well. Important to note that using these tools alone won’t guarantee the security of your application and it should be used as a part of a comprehensive security testing process.

Average CVSS score of open redirect vulnerability

The Common Vulnerability Scoring System (CVSS) is a method for scoring the severity of security vulnerabilities. The scores are based on a scale of 0-10, with 10 being the most severe.

Open Redirect vulnerabilities are generally considered to be of low-medium severity. The CVSS score for an open redirect vulnerability typically falls in the range of 2.6-4.3, but it might change depending on the specific scenario.

The reason for the low-medium severity is that the vulnerability itself does not directly lead to a security breach, but it can be used as a part of a larger attack scenario. For example, an attacker can use open redirect vulnerability to lure unsuspecting users to a phishing page or a malware distribution site.

CVSS score is a relative measure of the vulnerability severity and it should be used in conjunction with other factors, such as the business impact, the likelihood of exploit, and the availability of a solution, to determine the overall risk of a vulnerability.

The Common Weakness Enumeration (CWE)

The main CWE related to open redirect vulnerabilities is CWE-601: “URL Redirection to Untrusted Site (‘Open Redirect’)” which describes the scenario where an application redirects a user to an external web site without properly validating the destination URL.

However, open redirect vulnerabilities can also be a symptom of other CWEs such as:

CWE-601: URL Redirection to Untrusted Site – This weakness occurs when an application redirects a user to an external web site, but the application does not properly validate the destination URL. This allows attackers to redirect users to arbitrary sites, which can be used to phish for sensitive information, steal login credentials, or distribute malware.

CWE-918: Server-Side Request Forgery (SSRF) – This weakness occurs when an application makes a request to a back-end system or service, but the application does not properly validate the request. This allows attackers to send malicious requests to the back-end system or service, which can be used to access sensitive information, steal login credentials, or distribute malware. Open redirect vulnerabilities can be a symptom of SSRF, as an attacker can use an open redirect vulnerability to redirect a user to a malicious URL, which can then be used to trigger an SSRF vulnerability.

CWE-922: Improper Restriction of XML External Entities (XXE) – This weakness occurs when an application processes XML data, but the application does not properly restrict the use of external entities. This allows attackers to access sensitive information, steal login credentials, or distribute malware. Open redirect vulnerabilities can be a symptom of XXE, as an attacker can use an open redirect vulnerability to redirect a user to a malicious XML file, which can then be used to trigger an XXE vulnerability.

CWE-923: Improper Restriction of Excessive Authentication Attempts – This weakness occurs when an application allows an attacker to repeatedly attempt to authenticate, even after the attacker’s credentials have been invalidated. This allows attackers to guess login credentials. Open redirect vulnerabilities can be a symptom of this cwe, as an attacker can use an open redirect vulnerability to redirect a user to a malicious login page, which can then be used to trigger this vulnerability.

CWE-927: Improper Validation of Array Index – This weakness occurs when an application uses an array index, but the application does not properly validate the array index. This allows attackers to access sensitive information, steal login credentials, or distribute malware. Open redirect vulnerabilities can be a symptom of this cwe, as an attacker can use an open redirect vulnerability to redirect a user to a malicious page with a manipulated array index, which can then be used to trigger this vulnerability.

CWE-928: Improper Validation of User-Controlled Input – This weakness occurs when an application accepts user input, but the application does not properly validate the input. This allows attackers to inject malicious input, which can be used to access sensitive information, steal login credentials, or distribute malware. Open redirect vulnerabilities can be a symptom of this cwe, as an attacker can use an open redirect vulnerability to redirect a user to a malicious page with a manipulated user input, which can then be used to trigger this vulnerability.

CWE-929: Improper Control of Resource Identifiers – This weakness occurs when an application does not properly control access to resources, such as files or network connections. This allows attackers to access sensitive information, steal login credentials, or distribute malware. Open redirect vulnerabilities can be a symptom of this cwe, as an attacker can use an open redirect vulnerability to redirect a user to a malicious page that can then be used to trigger this vulnerability, by manipulating the URL or the parameters to access unauthorized resources.

CWE-935: Improper Neutralization of Special Elements used in a Command (‘Command Injection’) – This weakness occurs when an application passes user-controlled input to a command, but the application does not properly neutralize special elements that can be used to modify the command. This allows attackers to execute arbitrary commands, which can be used to access sensitive information, steal login credentials, or distribute malware. Open redirect vulnerabilities can be a symptom of this cwe, as an attacker can use an open redirect vulnerability to redirect a user to a malicious page that can then be used to trigger this vulnerability by injecting malicious commands in the URL or the parameters.

CWE-937: Improper Neutralization of Special Elements used in an OS Command (‘OS Command Injection’) – This weakness occurs when an application passes user-controlled input to an operating system command, but the application does not properly neutralize special elements that can be used to modify the command. This allows attackers to execute arbitrary commands with the privileges of the application, which can be used to access sensitive information, steal login credentials, or distribute malware. Open redirect vulnerabilities can be a symptom of this cwe, as an attacker can use an open redirect vulnerability to redirect a user to a malicious page that can then be used to trigger this vulnerability by injecting malicious commands in the URL or the parameters.

Important to note that open redirect vulnerabilities can also be related to other CWEs depending on the specific scenario, for example, if the vulnerability is caused by a lack of input validation or a lack of proper access controls, the CWE IDs would be CWE-20: Improper Input Validation or CWE-287: Improper Authentication respectively.

CWE-20: Improper Input Validation – This weakness occurs when an application does not properly validate user-controlled input, which allows attackers to inject malicious input. Improper input validation can lead to various types of vulnerabilities, including open redirect vulnerabilities. If an application does not validate the destination URL in a redirect function, an attacker can use the open redirect vulnerability to redirect a user to a malicious site.

CWE-287: Improper Authentication – This weakness occurs when an application does not properly authenticate users, which allows attackers to gain unauthorized access to resources. Improper authentication can lead to various types of vulnerabilities, including open redirect vulnerabilities. If an application does not properly authenticate the user before redirecting them, an attacker can use the open redirect vulnerability to redirect a user to a malicious site without proper authentication.

While these CWEs may be related to open redirect vulnerabilities, they may not be the direct cause of the vulnerability. It’s always important to thoroughly assess the root cause of the vulnerability to determine the appropriate CWE ID.

CWE list is constantly evolving and new entries are added or modified over time.

In summary, CWE-601 is the main CWE related to open redirect vulnerabilities, but open redirect vulnerabilities can also be a symptom of other CWEs such as CWE-918, CWE-922, CWE-923, CWE-927, CWE-928, CWE-929, CWE-935, CWE-937 and other CWEs depending on the specific scenario.

Open redirect vulnerability exploits

There are several popular exploits that are commonly used to exploit open redirect vulnerabilities.

Phishing: One of the most common ways to exploit an open redirect vulnerability is to redirect the user to a phishing website page that looks like a legitimate website, such as a bank or online store, in order to steal sensitive information such as login credentials, credit card information, and personal data.

Malware Distribution: An attacker can use an open redirect vulnerability to redirect a user to a site that distributes malware, which can then be used to compromise the user’s system.

Session Hijacking: An attacker can use an open redirect vulnerability to redirect a user to a malicious site, which can then be used to steal the user’s session cookies, allowing the attacker to take over the user’s session and access sensitive information.

Search Engine Optimization (SEO) Spam: An attacker can use an open redirect vulnerability to redirect a user to a site that is designed to improve the search engine ranking of another site.

Clickjacking: An attacker can use an open redirect vulnerability to redirect a user to a site that contains a hidden iframe, which can then be used to perform clickjacking attacks.

Redirect to a malicious website: An attacker can use the vulnerability to redirect users to a malicious website, which can be used to distribute malware or steal sensitive information.

Cross-site Scripting (XSS) attacks: An attacker can use an open redirect vulnerability to redirect a user to a site that contains a malicious script, which can then be used to steal sensitive information, such as login credentials.

Bypassing security controls: An attacker can use an open redirect vulnerability to bypass security controls, such as firewalls, intrusion detection systems, or web application firewalls, to gain unauthorized access to a system or network.

Practicing in test for open redirect vulnerability

One way to test for open redirect vulnerabilities is to use a vulnerable service or repository that has been specifically designed to be vulnerable to open redirect attacks.

OWASP WebGoat is a vulnerable web application that is specifically designed for security testing, it includes several vulnerabilities, including open redirect, that can be used to test the effectiveness of web application scanners and manual testing methods.

OWASP Juice Shop is another vulnerable web application that is specifically designed for security testing. It includes several vulnerabilities, including open redirect, that can be used to test the effectiveness of web application scanners and manual testing methods.

DVWA (Damn Vulnerable Web Application) is a PHP/MySQL web application that is damn vulnerable. Its main goal is to be an aid for security professionals to test their skills and tools in a legal environment, help web developers better understand the processes of securing web applications and aid teachers/students to teach/learn web application security in a class room environment.

The Mutillidae II is another vulnerable web application that is specifically designed for security testing. It includes several vulnerabilities, including open redirect, that can be used to test the effectiveness of web application scanners and manual testing methods.

For study open redirect vulnerability

There are several resources available to learn about open redirect vulnerabilities, including online courses, practice environments, and videos. Some of the resources you can use include:

OWASP (Open Web Application Security Project) offers several resources, including the OWASP Top 10 Project, which provides information on the top 10 most critical web application security risks, including open redirect vulnerabilities.

SANS Institute offers several online courses on web application security, including the SEC542 Web App Penetration Testing and Ethical Hacking course, which covers open redirect vulnerabilities.

Udemy, Coursera, and other e-learning platforms have many courses related to web application security, penetration testing and ethical hacking, some of them are free, others are paid but they can provide you with a comprehensive knowledge of open redirect vulnerabilities and how to test and defend against them.

YouTube has many educational videos on web application security, including open redirect vulnerabilities, some of them are made by security experts, others by students or enthusiasts that can help you understand the topic.

Practice platforms such as HackTheBox, TryHackMe, and others, provide a safe environment to practice and test your skills in web application security, including open redirect vulnerabilities.

Books with review of open redirect vulnerability

“The Web Application Hacker’s Handbook: Finding and Exploiting Security Flaws” by Dafydd Stuttard and Marcus Pinto: This book is considered as a classic in the field of web application security. It covers a wide range of web application vulnerabilities, including open redirect, and provides a detailed explanation of how to find and exploit these vulnerabilities.

“Web Application Security Testing Cookbook” by Paco Hope and Ben Walther: This book is a practical guide to web application security testing, providing step-by-step instructions for testing for various types of vulnerabilities, including open redirect vulnerabilities.

“Web Security Testing Cookbook: Systematic Techniques to Find Problems Fast” by Simon Bennetts: This book is a cookbook-style guide to web security testing, providing step-by-step instructions for testing for various types of vulnerabilities, including open redirect vulnerabilities.

“Web Hacking 101: How to Make Money Hacking Ethically” by Peter Yaworski : This book covers a wide range of web application vulnerabilities, including open redirect vulnerabilities, and provides a detailed explanation of how to find and exploit these vulnerabilities, and how to make money as a web application security researcher.

“Mastering Modern Web Penetration Testing” by Bullard, Chris: This book is a comprehensive guide to modern web penetration testing, covering the latest techniques and tools for finding and exploiting web application vulnerabilities, including open redirect vulnerabilities.

“Web Hacking: Attacks and Defense” by Stuttard Dafydd & Pinto Marcus: This book provides an in-depth look at web hacking and the various types of attacks that can be used to exploit web applications, including open redirect vulnerabilities. It also covers the tools and techniques used by attackers and provides guidance on how to defend against these attacks.

“Hacking Exposed Web Applications” by Joel Scambray, Mike Shema, and Caleb Sima: This book provides a comprehensive guide to web application security, including open redirect vulnerabilities. It covers both manual testing techniques and automated tools and provides practical guidance on how to defend against these types of attacks.

List of payloads suitable for open redirect vulnerabilities

There are several payloads that can be used to test for open redirect vulnerabilities, depending on the specific vulnerability and the type of attack that is being performed. Some examples of payloads that can be used to test for open redirect vulnerabilities include:

Basic payload: A basic payload is a URL that contains a malicious link, such as “http://example.com/redirect.php?url=http://evil.com

URL encoded payload: A URL encoded payload is a payload that uses URL encoding to encode special characters, such as “http://example.com/redirect.php?url=http%3A%2F%2Fevil.com

JavaScript payload: A JavaScript payload is a payload that uses JavaScript to redirect the user, such as “<script>window.location=’http://evil.com‘;</script>”

HTML payload: An HTML payload is a payload that uses HTML to redirect the user, such as “<meta http-equiv=’refresh’ content=’0;url=http://evil.com’>”

IP address payload: An IP address payload is a payload that uses an IP address to redirect the user, such as “http://example.com/redirect.php?url=http://192.168.1.1

File path payload : A payload that uses file path to redirect the user, such as “http://example.com/redirect.php?url=file:///etc/passwd

How to be protected from open redirect vulnerability

There are several ways to protect against open redirect vulnerabilities, including using firewall rules and Sigma rules. Sigma rules are a way to detect and alert on suspicious activity, while firewall rules are used to block traffic that matches specific criteria.

1. Firewall rules: Firewall rules can be used to block traffic to specific URLs or IP addresses that are known to be malicious. For example, a firewall rule could be created to block traffic to any URL that contains the string “<ins>http://evil.com</ins>”.

2. Sigma rules: Sigma rules can be used to detect and alert on suspicious activity, such as an excessive number of redirects to a specific URL or IP address. For example, a Sigma rule could be created to detect and alert on any redirect that contains the string “<ins>http://evil.com</ins>”.

3. WAF (Web Application Firewall) rules: WAF can help to protect against open redirect vulnerabilities by inspecting the incoming traffic and blocking any requests that contain malicious payloads or attempts to exploit open redirect vulnerabilities.

4. Input validation : Input validation is one of the best ways to protect against open redirect vulnerabilities. By validating the user input, you can ensure that the application only accepts valid URLs, and reject any URLs that contain malicious payloads.

5. Security Information and Event Management (SIEM) systems: SIEM systems can help to detect and alert on suspicious activity, such as an excessive number of redirects to a specific URL or IP address.

6. URL filtering services: These services can help to block traffic to specific URLs or IP addresses that are known to be malicious.

7. DNS-based filtering: DNS-based filtering can help to block traffic to specific URLs or IP addresses that are known to be malicious.

8. Network firewalls: Network firewalls can help to block traffic to specific URLs or IP addresses that are known to be malicious.

9. Content delivery networks (CDNs) : CDNs can help to protect against open redirect vulnerabilities by caching web pages and filtering out any requests that contain malicious payloads or attempts to exploit open redirect vulnerabilities.

10. Web proxy services : web proxy services can help to inspect the incoming traffic and blocking any requests that contain malicious payloads or attempts to exploit open redirect vulnerabilities.

11. Vulnerability scanners : Vulnerability scanners can help to detect open redirect vulnerabilities by crawling web applications and identifying any potential vulnerabilities.

Mitigations for open redirect vulnerability

There are several mitigation techniques that can be used to protect against open redirect vulnerabilities:

1. Input validation: One of the best ways to protect against open redirect vulnerabilities is by validating user input. By validating the user input, you can ensure that the application only accepts valid URLs and reject any URLs that contain malicious payloads.

2. Whitelisting: Whitelisting is a technique that can be used to only allow redirects to specific, known-good URLs.

3. Use of a Content Security Policy (CSP): A CSP is a security feature that can be used to prevent cross-site scripting (XSS) and other types of attacks by specifying which sources of content are allowed to be loaded by the browser.

4. Use of a token-based validation: Token-based validation is a technique that can be used to prevent open redirect vulnerabilities by ensuring that a token is included in the redirect URL, and that the token can only be used once.

5. Use of a referrer check: A referrer check is a technique that can be used to prevent open redirect vulnerabilities by checking the HTTP referrer header to ensure that the redirect request is coming from a trusted source.

6. Use of a Same-Origin Policy (SOP): The Same-Origin Policy is a security feature that prevents a web page from making requests to a different domain than the one that served the web page. This can help to prevent open redirect vulnerabilities by ensuring that redirects are only allowed to the same domain.

7. Use of a HTTP Strict Transport Security (HSTS): HSTS is a security feature that can be used to prevent open redirect vulnerabilities by ensuring that all communication with a web site is done over a secure, HTTPS connection.

8. Use of a Secure Cookies: Use of Secure flag and HttpOnly flag on cookies can prevent the attacker from stealing the cookie values by XSS and open redirect vulnerabilities.

Conclusion

Open redirect vulnerabilities are a serious security concern, and it’s essential to take the necessary steps to prevent them by validating user input, implementing security controls and using security services to detect and block malicious traffic. It’s also important to stay up to date with the latest vulnerabilities and mitigation techniques, and to test your systems regularly to ensure that they are secure.

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