CVE-2026-86344 Denial of service in Red Hat Directory Server 11
Unauthenticated attackers can exhaust worker threads in 389-ds-base by sending malformed LDAP sequences, causing a denial of service for all clients.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-86344?
CVE-2026-86344 is a high-severity denial of service vulnerability in Red Hat Directory Server 11, published on 1 Oct 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. An unauthenticated remote attacker can send a complete LDAP operation followed by the first bytes of an incomplete LDAPMessage on the same connection, causing the server to hand that connection to a second worker thread before the first worker's result is flushed. The second worker blocks until nsslapd-ioblocktimeout while holding the connection mutex, preventing delivery of the completed operation's result. Repeating this across a small number of connections proportional to the configured worker-thread pool size exhausts the entire pool under default configuration, denying service to all clients (anonymous and authenticated, plaintext and TLS) for as long as the attacker maintains the connections.
Weakness: CWE-400
Which versions are affected by CVE-2026-86344?
How do I fix CVE-2026-86344?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-86344 being exploited?
There is no known exploitation of CVE-2026-86344 in the wild and no public exploit code.
Sources
Also known as AZL-107951, DEBIAN-CVE-2026-86344, GHSA-62jf-8m49-534w, UBUNTU-CVE-2026-86344.