CVE-2026-79591 Use after free in n/a
A heap-buffer-overflow and use-after-free in libxls allows attackers to execute arbitrary code or cause denial of service via crafted files.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-79591?
CVE-2026-79591 is a high-severity use after free vulnerability in n/a, published on 10 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
A heap-buffer-overflow and use-after-free vulnerability exists in the xls_getCSS() function of libxls 1.6.3 due to insufficient validation of a file-controlled font index.
Weakness: CWE-122
Which versions are affected by CVE-2026-79591?
How do I fix CVE-2026-79591?
Upgrade to a fixed version.
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-2026-79591 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-79591 exists.
Sources
Also known as DEBIAN-CVE-2026-79591, GHSA-8cvq-g9xh-jmpf, UBUNTU-CVE-2026-79591.