The authentication service of the extension does not verify the OpenID Connect authentication state from the user lookup chain. Instead, the authentication service authenticates every valid frontend user from the user lookup chain, where the frontend user field “tx_oidc” is not empty.

In scenarios, where either ext:felogin is active or where $GLOBALS['TYPO3_CONF_VARS'][‘FE’][‘checkFeUserPid’] is disabled, an attacker can login to OpenID Connect frontend user accounts by providing a valid username and any password.

References

• https://github.com/FriendsOfPHP/security-advisories/blob/master/causal/oidc/CVE-2024-30173.yaml
• https://typo3.org/security/advisory/typo3-ext-sa-2024-002