Description
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
Open Redirect Guide
Read our in-depth guide on exploiting and mitigating this weakness
Potential Impact
Access Control
Bypass Protection Mechanism, Gain Privileges or Assume Identity
Access Control, Confidentiality, Other
Bypass Protection Mechanism, Gain Privileges or Assume Identity, Other
Demonstrative Examples
$redirect_url = $_GET['url'];header("Location: " . $redirect_url);http://example.com/example.php?url=http://malicious.example.compublic class RedirectServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String query = request.getQueryString();if (query.contains("url")) {String url = request.getParameter("url");response.sendRedirect(url);}}
}<a href="http://bank.example.com/redirect?url=http://attacker.example.net">Click here to log in</a>Mitigations & Prevention
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across relat
Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. For example, ID 1 could map to "/login.asp" and ID 2 could map to "http://www.example.com/". Features such as the ESAPI AccessReferenceMap [REF-45] provide this capability.
Ensure that no externally-supplied requests are honored by requiring that all redirect requests include a unique nonce generated by the application [REF-483]. Be sure that the nonce is not predictable (CWE-330).
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls. Many open redirect problems occur because the programmer assumed th
Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
Detection Methods
- Manual Static Analysis High — Since this weakness does not typically appear frequently within a single software package, manual white box techniques may be able to provide sufficient code coverage and reduction of false positives if all potentially-vulnerable operations can be assessed within limited time constraints.
- Automated Dynamic Analysis — Automated black box tools that supply URLs to every input may be able to spot Location header modifications, but test case coverage is a factor, and custom redirects may not be detected.
- Automated Static Analysis — Automated static analysis tools may not be able to determine whether input influences the beginning of a URL, which is important for reducing false positives.
- Automated Static Analysis High — Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then sea
- Automated Static Analysis - Binary or Bytecode High — According to SOAR [REF-1479], the following detection techniques may be useful:
- Dynamic Analysis with Automated Results Interpretation High — According to SOAR [REF-1479], the following detection techniques may be useful:
Real-World CVE Examples
| CVE ID | Description |
|---|---|
| CVE-2005-4206 | URL parameter loads the URL into a frame and causes it to appear to be part of a valid page. |
| CVE-2008-2951 | An open redirect vulnerability in the search script in the software allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via a URL as a parameter to the proper |
| CVE-2008-2052 | Open redirect vulnerability in the software allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via a URL in the proper parameter. |
| CVE-2020-11053 | Chain: Go-based Oauth2 reverse proxy can send the authenticated user to another site at the end of the authentication flow. A redirect URL with HTML-encoded whitespace characters can bypass the valida |
Related Weaknesses
Taxonomy Mappings
- WASC: 38 — URl Redirector Abuse
- Software Fault Patterns: SFP24 — Tainted input to command
Frequently Asked Questions
What is CWE-601?
CWE-601 (URL Redirection to Untrusted Site ('Open Redirect')) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
How can CWE-601 be exploited?
Attackers can exploit CWE-601 (URL Redirection to Untrusted Site ('Open Redirect')) to bypass protection mechanism, gain privileges or assume identity. This weakness is typically introduced during the Architecture and Design, Implementation phase of software development.
How do I prevent CWE-601?
Key mitigations include: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not stric
What is the severity of CWE-601?
CWE-601 is classified as a Base-level weakness (Medium abstraction). It has been observed in 4 real-world CVEs.