CVE-2026-104039 Sssd: sssd: denial of service via stale connection state reuse in pam gssapi responder
A local attacker can cause a denial of service in SSSD by triggering a use-after-free in the PAM GSSAPI responder, crashing the authentication service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-104039?
CVE-2026-104039 is a medium-severity use after free vulnerability in Red Hat Enterprise Linux 10, published on 6 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A flaw was found in SSSD. A local user can cause a denial of service (DoS) by disrupting system authentication services. When handling Generic Security Services Application Programming Interface (GSSAPI) authentication in the Pluggable Authentication Module (PAM) responder, cached connection state is freed upon completion without clearing the reference pointer. An attacker can exploit this by sending an additional request over the same connection, causing the service to access invalid memory and unexpectedly terminate.
Weakness: CWE-825
Which versions are affected by CVE-2026-104039?
How do I fix CVE-2026-104039?
No fix has been published for CVE-2026-104039 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-104039 being exploited?
There is no known exploitation of CVE-2026-104039 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-104039, GHSA-6ffw-v8mm-gqgh, UBUNTU-CVE-2026-104039.