CVE-2026-125197 FFmpeg through 9.0.2 Heap Out-of-Bounds Read via LCL/ZLIB Multithread Decoding

Medium 6.9 Published 9 Nov 2026 Updated 9 Nov 2026

Exploited in the wild: Not known
Fix: None listed

What is CVE-2026-125197?

CVE-2026-125197 is a medium-severity vulnerability in FFmpeg, published on 9 Nov 2026.

Official description

FFmpeg through 9.0.2 contains an integer underflow in decode_frame() in libavcodec/lcldec.c that allows attackers to trigger a heap out-of-bounds read via short ZLIB packets with FLAG_MULTITHREAD. Attackers can supply a crafted AVI or MKV file with an LCL video stream whose packet is shorter than 8 bytes, bypassing length clamping to crash the decoding application.

Weakness: CWE-191

Which versions are affected by CVE-2026-125197?

How do I fix CVE-2026-125197?

No fix has been published for CVE-2026-125197 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-125197 being exploited?

There is no known exploitation of CVE-2026-125197 in the wild and no public exploit code.

Sources

Also known as GHSA-82jp-g685-6p37, UBUNTU-CVE-2026-125197.