CWE-601

URL Redirection to Untrusted Site ('Open Redirect')

Base EXPLOIT LIKELIHOOD: LOW

What it is

The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.

Impact

Access Control	Bypass Protection Mechanism, Gain Privileges or Assume Identity
Access Control, Confidentiality, Other	Bypass Protection Mechanism, Gain Privileges or Assume Identity, Other

Mitigations

[Implementation]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 r
[Architecture and Design] 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.
[Architecture and Design]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.
[Architecture and Design] 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).
[Architecture and Design, Implementation]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 thro
[Operation] 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].

Real-world CVE examples

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 attack
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 prope
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 whi

Related weaknesses

CWE-610 (childof)

Test & detect

Browse all common weaknesses, check related exploited CVEs, or map to ATT&CK techniques.

Source: MITRE CWE. View on cwe.mitre.org →