CVE-2026-3979 quickjs-ng quickjs quickjs.c js_iterator_concat_return use after free
A local attacker can exploit a use-after-free flaw in the quickjs-ng JavaScript engine to potentially execute arbitrary code or cause a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-3979?
CVE-2026-3979 is a medium-severity use after free vulnerability in quickjs-ng quickjs, published on 12 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A flaw has been found in quickjs-ng quickjs up to 0.12.1. This affects the function js_iterator_concat_return of the file quickjs.c. This manipulation causes use after free. The attack requires local access. The exploit has been published and may be used. Patch name: daab4ad4bae4ef071ed0294618d6244e92def4cd. Applying a patch is the recommended action to fix this issue.
Which versions are affected by CVE-2026-3979?
How do I fix CVE-2026-3979?
No fix has been published for CVE-2026-3979 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-2026-3979 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-3979 exists.
Sources
Also known as GHSA-gr63-2w3v-w2gp, UBUNTU-CVE-2026-3979.