# CVE-2026-86344: 389-ds-base: 389-ds-base: unauthenticated worker-thread-pool exhaustion via completed-operation-then-incomplete-pdu connection requeue

Status: published. Published: 2026-10-01. Updated: 2026-11-04.

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.

## Remediation

- workaround: As an interim mitigation, administrators can limit the number of concurrent connections permitted per source IP address in front of the LDAP listener (for example via a firewall, load balancer, or a tool such as fail2ban), since exploitation requires several simultaneous connections from the same attacker. Upgrading to a fixed package remains the only complete resolution. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Directory Server 11 (389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Directory Server 11 (redhat-ds:11/389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Directory Server 12 (389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Directory Server 12 (redhat-ds:12/389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Directory Server 13 (389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10 (389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (389-ds:1.4/389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (389-ds-base): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (389-ds-base): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 0.35% as of 2026-11-04; percentile 28.47%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-400

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-86344 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2529329 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-86344; retrieved 2026-11-05; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-86344; retrieved 2026-11-05; source updated Not reported

Revision: 2dbfc44727064fb65b5577bf797194c1ad314c8b0f06326d1e3c4f62df7993c2

Canonical: https://y2.dev/cve/CVE-2026-86344

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