CVE-2026-86344
389-ds-base: 389-ds-base: unauthenticated worker-thread-pool exhaustion via completed-operation-then-incomplete-pdu connection requeue
What happened?
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.
Affected software and versions
| Software | Version information | Fixed version |
|---|---|---|
| 389-ds-baseRed Hat | Default status: affected | See vendor advisory |
| redhat-ds:11/389-ds-baseRed Hat | Default status: affected | See vendor advisory |
| 389-ds-baseRed Hat | Default status: affected | See vendor advisory |
| redhat-ds:12/389-ds-baseRed Hat | Default status: affected | See vendor advisory |
| 389-ds-baseRed Hat | Default status: affected | See vendor advisory |
| 389-ds-baseRed Hat | Default status: affected | See vendor advisory |
| 389-ds-baseRed Hat | Default status: unknown | See vendor advisory |
| 389-ds-baseRed Hat | Default status: unknown | See vendor advisory |
| 389-ds:1.4/389-ds-baseRed Hat | Default status: affected | See vendor advisory |
| 389-ds-baseRed Hat | Default status: affected | See vendor advisory |
| 389-ds-baseRed Hat | Default status: affected | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.