Executive brief
A vulnerability in the System Security Services Daemon (SSSD), a service that manages access to remote directories and authentication mechanisms, can cause the system's authentication component to crash when using a YubiKey or smartcard. This issue can be triggered by a local attacker to cause a denial of service, preventing users from logging in, or potentially to gain elevated privileges on the system. The flaw occurs during the authentication process when memory is incorrectly handled after a request is cancelled or completed.
Technical details
A use-after-free vulnerability exists in the SSSD PAM responder within the 'sss_certmap_match_cert' function. The root cause is that the 'sss_certmap_ctx' structure is owned by the PAM request state; if a request is cancelled or completes while the asynchronous 'p11_child' process is still running, the context is freed. When the child process eventually returns, 'parse_p11_child_response' attempts to use the dangling pointer, which may have been overwritten by certificate label data (e.g., "X.509 Certificate for PIV Authentication"). A local attacker with the ability to manipulate smartcard or YubiKey contents can trigger a crash (Denial of Service) or potentially influence memory to achieve privilege escalation.
Affected products
- Red Hat Enterprise Linux 10 affected
- Red Hat Enterprise Linux 8 affected
- Red Hat Enterprise Linux 9 affected
- SSSD sssd
Timeline
- 2026-06-09: other: Issue reported on SSSD GitHub repository
- 2026-06-18: other: Bug reported to Red Hat Bugzilla
- 2026-06-30: disclosed: CVE published