An open redirect vulnerability existed in MISP UsersController::routeafterlogin() because the value stored in the pre_login_requested_url session key was used as the post-login redirect destination without sufficiently enforcing that it was a local application path.
An unauthenticated remote attacker could craft a link that causes a victim to visit a trusted MISP instance and, after successful authentication, be redirected to an attacker-controlled external URL. This could be abused to increase the credibility of phishing attacks, redirect users to counterfeit login pages, or deliver attacker-controlled content from an untrusted domain. CWE-601 describes this weakness as accepting user-controlled input that specifies an external link and using it in a redirect, with phishing as a common consequence.
The patch mitigates the issue by decoding and parsing the URL, rejecting URLs with a scheme, host, user component, missing or non-local path, and protocol-relative forms such as //example.com and /example.com.
Weakness
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Misp | Misp-project | * | 2.5.39 (excluding) |
Potential Mitigations
- 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 related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Use a list of approved URLs or domains to be used for redirection.
- 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.
- 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 that certain inputs could not be modified, such as cookies and hidden form fields.