CWE-601: URL Redirection to Untrusted Site ('Open Redirect')

Detection Methods

Method

Automated Dynamic Analysis

Description

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.

Method

Automated Static Analysis

Description

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.

Method

Automated Static Analysis - Binary or Bytecode

Description

According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective: Bytecode Weakness Analysis - including disassembler + source code weakness analysis Binary Weakness Analysis - including disassembler + source code weakness analysis

Effectiveness

High

Method

Dynamic Analysis with Automated Results Interpretation

Description

According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective: Web Application Scanner Web Services Scanner Database Scanners

Effectiveness

High

Method

Dynamic Analysis with Manual Results Interpretation

Description

According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective: Fuzz Tester Framework-based Fuzzer

Effectiveness

High

Method

Manual Static Analysis - Source Code

Description

According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective: Manual Source Code Review (not inspections)

Effectiveness

High

Method

Automated Static Analysis - Source Code

Description

According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective: Source code Weakness Analyzer Context-configured Source Code Weakness Analyzer

Effectiveness

High

Method

Architecture or Design Review

Description

According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective: Formal Methods / Correct-By-Construction Cost effective for partial coverage: Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Effectiveness

High

Code Examples & CVEs

Demonstrative Examples

The following code obtains a URL from the query string and then redirects the user to that URL.

The problem with the above code is that an attacker could use this page as part of a phishing scam by redirecting users to a malicious site. For example, assume the above code is in the file example.php. An attacker could supply a user with the following link:

BadPHP

$redirect_url = $_GET['url'];header("Location: " . $redirect_url);

The following code is a Java servlet that will receive a GET request with a url parameter in the request to redirect the browser to the address specified in the url parameter. The servlet will retrieve the url parameter value from the request and send a response to redirect the browser to the url address.

The problem with this Java servlet code is that an attacker could use the RedirectServlet as part of an e-mail phishing scam to redirect users to a malicious site. An attacker could send an HTML formatted e-mail directing the user to log into their account by including in the e-mail the following link:

BadJava

public 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);}}                      }

AttackHTML

<a href="http://bank.example.com/redirect?url=http://attacker.example.net">Click here to log in</a>

Observed CVE Examples (4)

CVE-2005-4206

URL parameter loads the URL into a frame and causes it to appear to be part of a valid page.

View Details

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 function.

View Details

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.

View Details

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 validation (CWE-1289) to redirect to a malicious site (CWE-601)

View Details

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-601 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-601, URL Redirection to Untrusted Site ('Open Redirect'), throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Apply Input Validation controls for URL Redirection to Untrusted Site ('Open Redirect')

MITRE associates mitigation with Implementation, Architecture and Design, and Operation; the listed strategies include Input Validation, Enforcement by Conversion, Attack Surface Reduction, and Firewall; documented detection approaches include Manual Static Analysis, Automated Dynamic Analysis, Automated Static Analysis, and Automated Static Analysis - Binary or Bytecode. Use these source-defined anchors to turn CWE-601 into implementation, review, and verification checks for the affected component.

CWE-601: URL Redirection to Untrusted Site ('Open Redirect') — MITRE CWE

Triage CWE-601 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-601, URL Redirection to Untrusted Site ('Open Redirect'), has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-601

Apply MITRE's full root-cause mapping guidance when using CWE-601, URL Redirection to Untrusted Site ('Open Redirect'). Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-601 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-601, URL Redirection to Untrusted Site ('Open Redirect'). Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-601: URL Redirection to Untrusted Site ('Open Redirect')?+

CWE-601: URL Redirection to Untrusted Site ('Open Redirect') is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.

What are the security consequences of URL Redirection to Untrusted Site ('Open Redirect')?+

If exploited, CWE-601 (URL Redirection to Untrusted Site ('Open Redirect')) it can compromise Access Control, Confidentiality and Other, leading to outcomes such as Bypass Protection Mechanism, Gain Privileges or Assume Identity and Other.

How do you prevent or mitigate URL Redirection to Untrusted Site ('Open Redirect')?+

Recommended mitigations for CWE-601 include: 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. 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).

How is URL Redirection to Untrusted Site ('Open Redirect') detected?+

CWE-601 can be detected using Automated Dynamic Analysis, Automated Static Analysis, Automated Static Analysis - Binary or Bytecode, Dynamic Analysis with Automated Results Interpretation, Dynamic Analysis with Manual Results Interpretation and Manual Static Analysis - Source Code. Combining automated tooling with manual review typically yields the best coverage.

Which programming languages are affected by URL Redirection to Untrusted Site ('Open Redirect')?+

CWE-601 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of URL Redirection to Untrusted Site ('Open Redirect')?+

MITRE documents real CVEs mapped to CWE-601, including CVE-2005-4206, CVE-2008-2951, CVE-2008-2052 and CVE-2020-11053. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-601 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-601: URL Redirection to Untrusted Site ('Open Redirect')

Technical Details

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Code Examples & CVEs

Demonstrative Examples

Observed CVE Examples (4)

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-601 with SSDF evidence

Apply Input Validation controls for URL Redirection to Untrusted Site ('Open Redirect')

Triage CWE-601 against known exploitation evidence

Apply precise root-cause mapping to CWE-601

Validate CWE-601 with root-cause mapping checks

Frequently Asked Questions

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