Zitadel is open-source identity infrastructure software. Prior to 4.6.0, 3.4.3, and 2.71.18, a potential vulnerability exists in ZITADEL's password reset mechanism. ZITADEL utilizes the Forwarded or X-Forwarded-Host header from incoming requests to construct the URL for the password reset confirmation link.

This link, containing a secret code, is then emailed to the user. If an attacker can manipulate these headers (e.g., via host header injection), they could cause ZITADEL to generate a password reset link pointing to a malicious domain controlled by the attacker. If the user clicks this manipulated link in the email, the secret reset code embedded in the URL can be captured by the attacker.

This captured code could then be used to reset the user's password and gain unauthorized access to their account. It's important to note that this specific attack vector is mitigated for accounts that have Multi-Factor Authentication (MFA) or Passwordless authentication enabled. This vulnerability is fixed in 4.6.0, 3.4.3, and 2.71.18.