MISP: HTTP Method Bypass of Login Security Controls (Bruteforce Protection and Email OTP)

The login() function in MISP's UsersController.php contained insufficient HTTP method validation for several security-critical code paths. The original code used an allowlist approach, checking only for specific HTTP methods (POST and PUT) before enforcing bruteforce protection, email one-time-password (OTP) verification, and login-failure logging. Because the checks were not exhaustive, an unauthenticated attacker could issue login requests using other HTTP methods and bypass all three security controls simultaneously. Specifically: 

 - the bruteforce blocklisting check and attempt counter were skipped, allowing unlimited credential-guessing attempts without being rate-limited or blocked
 -  the email OTP two-factor authentication step was skipped, defeating the second factor of authentication
 - login-failure events were neither logged nor counted, removing the audit trail and the mechanism that would normally trigger a blocklist entry.

The security impact is the effective disabling of brute-force protection and multi-factor authentication for any attacker who can craft an HTTP request with a non-POST/PUT method to the login endpoint, potentially leading to credential compromise and unauthorized access to the MISP instance.

Version affected: <2.5.47