CVE-2026-18663 Use after free in Red Hat Directory Server 11
An unauthenticated remote attacker can cause a double-free and denial of service in 389-ds-base by sending a specific BIND request.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-18663?
CVE-2026-18663 is a medium-severity use after free vulnerability in Red Hat Directory Server 11, published on 12 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A flaw was found in 389-ds-base. The get_ldapmessage_controls_ext() function frees the parsed controls array on the Session Tracking critical-control rejection path without clearing the SLAPI_REQCONTROLS pblock slot. Operation teardown then frees the same pointer again, causing a double-free. An unauthenticated remote attacker can trigger this with a single BIND request carrying a critical Session Tracking control, resulting in heap corruption and potential denial of service.
Weakness: CWE-415
Which versions are affected by CVE-2026-18663?
How do I fix CVE-2026-18663?
Apply the vendor's patch.
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-2026-18663 being exploited?
There is no known exploitation of CVE-2026-18663 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-18663, GHSA-m545-9vp4-qjrp, UBUNTU-CVE-2026-18663.