Summary
phpMyFAQ contains an authentication bypass in its Keycloak and Entra ID single sign-on callbacks that can allow an IdP-authenticated user to skip TOTP two-factor authentication. If an attacker controls or compromises an identity linked to a 2FA-enabled account, including an administrator account, the completed OIDC flow may provide a fully authenticated session.
phpMyFAQ contains an authentication bypass in its Keycloak and Entra ID single sign-on callbacks that can allow an IdP-authenticated user to skip TOTP two-factor authentication. If an attacker controls or compromises an identity linked to a 2FA-enabled account, including an administrator account, the completed OIDC flow may provide a fully authenticated session.
Affected context
The issue occurs in phpMyFAQ deployments that:
- Enable Keycloak or Entra ID OIDC single sign-on
- Link IdP identities to local phpMyFAQ accounts
- Require TOTP for those accounts
- Process SSO callbacks without adequately enforcing the local account's second-factor requirement
Risk is greatest when privileged accounts are accessible through the affected SSO integration.
The issue occurs in phpMyFAQ deployments that:
- Enable Keycloak or Entra ID OIDC single sign-on
- Link IdP identities to local phpMyFAQ accounts
- Require TOTP for those accounts
- Process SSO callbacks without adequately enforcing the local account's second-factor requirement
Risk is greatest when privileged accounts are accessible through the affected SSO integration.
Exploit preconditions
- Attack surface: Keycloak or Entra ID OIDC callback handling
- Required access: A valid or compromised IdP identity associated with a phpMyFAQ account
- Trigger point: Completion of the SSO callback and session establishment
- Why exploitation is possible: The callback can treat successful IdP authentication as sufficient for a fully authenticated session without consistently requiring the account's TOTP factor
- Attack surface: Keycloak or Entra ID OIDC callback handling
- Required access: A valid or compromised IdP identity associated with a phpMyFAQ account
- Trigger point: Completion of the SSO callback and session establishment
- Why exploitation is possible: The callback can treat successful IdP authentication as sufficient for a fully authenticated session without consistently requiring the account's TOTP factor
Why this happens
The underlying flaw is an authentication-state validation failure. The SSO callback establishes a session after validating the external identity but does not preserve or enforce the requirement for a configured local second factor before granting full authentication. This behavior maps to CWE-287: Improper Authentication, because the application accepts an incomplete authentication process as proof of the user's full identity and authorization state.
The underlying flaw is an authentication-state validation failure. The SSO callback establishes a session after validating the external identity but does not preserve or enforce the requirement for a configured local second factor before granting full authentication. This behavior maps to CWE-287: Improper Authentication, because the application accepts an incomplete authentication process as proof of the user's full identity and authorization state.
Potential impact
- An attacker may bypass TOTP protection for a linked account.
- An attacker could obtain a fully authenticated phpMyFAQ session.
- Administrative accounts may be taken over if their IdP identities are compromised.
- An attacker may access, alter, or delete protected knowledge-base content.
- The incident could enable further abuse of connected identity or application resources.
- An attacker may bypass TOTP protection for a linked account.
- An attacker could obtain a fully authenticated phpMyFAQ session.
- Administrative accounts may be taken over if their IdP identities are compromised.
- An attacker may access, alter, or delete protected knowledge-base content.
- The incident could enable further abuse of connected identity or application resources.
General mitigation guidance
Mitigation generally focuses on making multi-factor authentication state explicit and mandatory across every authentication path.
Common defensive patterns include:
- Require successful TOTP verification before issuing a fully privileged session, including after OIDC callbacks.
- Represent partially authenticated and fully authenticated states separately.
- Apply the same second-factor policy to SSO, local login, account linking, recovery, and session refresh flows.
- Validate issuer, audience, nonce, state, token claims, and account-linking rules for OIDC responses.
- Use secure-by-default settings that do not silently downgrade MFA requirements for federated users.
- Minimize administrative privileges and require stronger controls for privileged accounts.
- Record and alert on SSO sessions that reach privileged functionality without a corresponding second-factor event.
Mitigation generally focuses on making multi-factor authentication state explicit and mandatory across every authentication path.
Common defensive patterns include:
- Require successful TOTP verification before issuing a fully privileged session, including after OIDC callbacks.
- Represent partially authenticated and fully authenticated states separately.
- Apply the same second-factor policy to SSO, local login, account linking, recovery, and session refresh flows.
- Validate issuer, audience, nonce, state, token claims, and account-linking rules for OIDC responses.
- Use secure-by-default settings that do not silently downgrade MFA requirements for federated users.
- Minimize administrative privileges and require stronger controls for privileged accounts.
- Record and alert on SSO sessions that reach privileged functionality without a corresponding second-factor event.
How teams detect issues like this
High-level detection approaches include:
- Static analysis and code review for callback handlers that create full sessions immediately after IdP validation.
- Searching for authentication branches where MFA or TOTP checks are absent, optional, or bypassed for SSO users.
- Reviewing session-state models for a clear distinction between identity verification and second-factor completion.
- Testing each supported login, account-linking, recovery, and session-renewal path against the organization's MFA policy.
- Enforcing policy checks in CI and automated security review tools to prevent authentication flows from omitting required factors.
- Monitoring identity-provider and application logs for privileged SSO sessions without successful TOTP verification.
High-level detection approaches include:
- Static analysis and code review for callback handlers that create full sessions immediately after IdP validation.
- Searching for authentication branches where MFA or TOTP checks are absent, optional, or bypassed for SSO users.
- Reviewing session-state models for a clear distinction between identity verification and second-factor completion.
- Testing each supported login, account-linking, recovery, and session-renewal path against the organization's MFA policy.
- Enforcing policy checks in CI and automated security review tools to prevent authentication flows from omitting required factors.
- Monitoring identity-provider and application logs for privileged SSO sessions without successful TOTP verification.
