CVE-2026-57589 Use after free in OpenBSD

High 7.4 Published 25 Jun 2026 Updated 26 Jun 2026

A use-after-free in the OpenBSD kernel allows local attackers to escalate privileges to root via a race condition in sys_semget.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-57589?

CVE-2026-57589 is a high-severity use after free vulnerability in Openbsd Openbsd, published on 25 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

sys/kern/sysv_sem.c in OpenBSD through 7.9 has a use-after-free allowing local privilege escalation to root. This is a context switch use-after-free after tsleep in sys_semget().

Weakness: CWE-416

Which versions are affected by CVE-2026-57589?

It affects 1 product.

Products include Openbsd Openbsd.

How do I fix CVE-2026-57589?

No fix has been published for CVE-2026-57589 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-2026-57589 being exploited?

There is no known exploitation of CVE-2026-57589 in the wild and no public exploit code.

All Openbsd Openbsd vulnerabilities

Sources

Also known as GHSA-w3gf-4959-2377.