CVE-2026-91819 in MISP
Summary
by MITRE • 09/15/2026
Affected versions of MISP rely on CakePHP request-method override processing in a way that can disable CSRF and form-security validation.
CakePHP honors a _method field or X-HTTP-Method-Override header by rewriting the effective request method. For override values outside the normal write verbs POST, PUT, PATCH, and DELETE, CakePHP also clears the parsed request body. MISP’s security component then determines whether to perform _validatePost() and _validateCsrf() based on whether request data remains. With a value such as:
_method=GET
the body becomes empty before those checks run, so both protections are skipped. A cross-site form containing only that override can therefore reach actions whose parameters are taken from the URL rather than the request body
Version affected: ≤2.5.45
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability in MISP versions up to 2.5.45 stems from a flawed interaction between the application framework, CakePHP, and MISP’s own security middleware regarding HTTP method override handling. CakePHP is designed to support RESTful conventions by allowing clients to specify an intended HTTP method via the _method query parameter or the X-HTTP-Method-Override header. When such an override is detected for methods other than standard write verbs like POST, PUT, PATCH, and DELETE, CakePHP automatically clears the parsed request body to prevent ambiguity in data handling. This behavior is generally safe for stateless operations but introduces a critical logic flaw when combined with MISP’s security component.
MISP relies on its security component to enforce Cross-Site Request Forgery (CSRF) protection and form validation through methods such as _validateCsrf() and _validatePost(). These checks are conditionally executed based on the presence of request data in the body. Because CakePHP clears the body when a non-standard method override is used, MISP’s security component incorrectly interprets this empty state as an indication that no sensitive form submission has occurred. Consequently, it skips both CSRF token verification and post-data validation entirely. This logic error effectively disables two layers of defense against unauthorized actions for any endpoint that accepts parameters via the URL query string rather than the request body.
The operational impact of this vulnerability is significant because it allows attackers to bypass CSRF protections using a simple cross-site form submission. An attacker can craft a malicious webpage containing an HTML form with a hidden field setting _method=GET or similar override values. When a victim authenticated in MISP visits this page, the browser sends the request with the overridden method and empty body. The server processes this as a GET-like operation without validating the CSRF token, allowing the attacker to trigger state-changing actions if those actions also accept parameters via URL query strings. While many critical functions in MISP may require POST data for full exploitation, any functionality that relies on URL-based parameters becomes vulnerable to unauthorized execution due to the disabled security checks.
This flaw aligns with CWE-352, which describes Cross-Site Request Forgery (CSRF), specifically where the application fails to properly validate request origins or tokens under specific input conditions. It also relates to CWE-694, Use of Redundant Connections, in a logical sense where redundant processing paths lead to security bypasses, though more accurately it reflects CWE-20 Improper Input Validation as the system incorrectly validates the absence of body data as safe for skipping checks. From an ATT&CK perspective, this vulnerability facilitates T1566.001 Spearphishing Link or T1566.002 Spearphishing Attachment if used in conjunction with social engineering to lure users into triggering the malicious form.
Mitigation strategies must address both the framework configuration and application logic. The most effective immediate mitigation is upgrading MISP to version 2.5.46 or later, where this specific interaction between CakePHP’s method override behavior and MISP’s security component has been corrected. For environments unable to upgrade immediately, administrators should disable HTTP method overrides in the web server or PHP configuration if not strictly required by legitimate API consumers. Additionally, reviewing custom modules or plugins within MISP that rely on URL parameters for sensitive operations is recommended, ensuring they implement explicit CSRF validation regardless of request body presence. Developers should also avoid relying solely on the existence of POST data to determine whether security checks are necessary; instead, all state-changing requests should unconditionally enforce CSRF token verification and input sanitization independent of method override behaviors.