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GHSA-v8hx-4vx8-wc96
No affected components available
Summary
Two-factor authentication (TOTP) can be fully bypassed for the REST API. The KIMAI_SESSION cookie returned in the response to the login request; issued after only the password is verified, before the TOTP step; is already accepted as authenticated by every /api/* endpoint.
So after submitting just the password, the web UI correctly holds the browser at the TOTP screen (/en/auth/2fa), but the cookie from that same login response can be replayed against the API to act as the user without ever entering the second factor. This affects any account with 2FA enabled and requires only the account password.
Details
Affected Component
- The API firewall / authorization.
config/packages/security.yaml guards the API with { path: '^/api', roles: IS_AUTHENTICATED }. During 2FA the session carries a Scheb TwoFactorToken, which satisfies IS_AUTHENTICATED (it is a real, non-anonymous token). App\API\Authentication\ApiRequestMatcher returns !$request->hasPreviousSession(), so a request that carries the login session skips the stateless API firewall and is served by the main session firewall; Scheb's TwoFactorAccessDecider::isAccessible() then evaluates IS_AUTHENTICATED to true for ^/api and lets it through, and App\Voter\ApiVoter grants API to any token whose user is a User. Web routes are not affected because they require concrete roles (e.g. ROLE_USER) that a TwoFactorToken does not hold.
PoC
A PoC was provided, but removed for security reasons.
Impact
Two-factor authentication provides no protection for the REST API. If an attacker obtains a user's password (phishing, credential stuffing, reuse, breach); exactly the threat 2FA is meant to defend against; they get full authenticated API access as that user without the second factor. The whole exploit is a single cookie taken from the login response; no API token, Bearer header or CSRF token is required.
Solution
- The
/api/firewall now usesIS_AUTHENTICATED_REMEMBEREDwhich is only assigned after 2FA. The historically usedIS_AUTHENTICATEDflag is applied immediately after login and before 2FA happened. - The APIVoter checks both
$token instanceof TwoFactorTokenInterfaceandisGranted('IS_AUTHENTICATED_2FA_IN_PROGRESS', $user)to make sure that the user is not currently in the 2FA step. - Regression tests were added to prevent future escalation of the same issue.
See https://www.kimai.org/en/security/ghsa-v8hx-4vx8-wc96 for more information.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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