CVE-2026-66038 FFmpeg LCL/ZLIB Video Decoder Information Disclosure via lcldec.c
Attackers can expose uninitialized heap memory via crafted video streams, potentially leaking sensitive data and defeating ASLR in media processing services.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-66038?
CVE-2026-66038 is a high-severity vulnerability in Ffmpeg Ffmpeg, published on 24 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
FFmpeg through 8.1.2, fixed in commit 8670835, contains an information disclosure vulnerability in the LCL/ZLIB video decoder that allows attackers to expose uninitialized heap memory by supplying a valid zlib stream that inflates to fewer bytes than the expected frame size. The zlib_decomp() function in lcldec.c treats short decompression as non-fatal and continues to the RGB24 conversion path, which copies a full frame's worth of rows from the allocation buffer using original frame dimensions, causing uninitialized heap contents including pointer-derived allocator bytes to be copied into the attacker-observable AVFrame output and potentially defeating ASLR in long-lived media processing services.
Weakness: CWE-908
Which versions are affected by CVE-2026-66038?
It affects 1 product.
Products include Ffmpeg Ffmpeg.
How do I fix CVE-2026-66038?
Apply the vendor's patch.
Is CVE-2026-66038 being exploited?
There is no known exploitation of CVE-2026-66038 in the wild and no public exploit code.
Other vulnerabilities in Ffmpeg Ffmpeg
Sources
Also known as DEBIAN-CVE-2026-66038, ECHO-9db0-dfd3-a7bb, GHSA-8mx4-8xfc-qr43, JLSEC-2026-1184, MINI-xp5m-j82j-47c8, UBUNTU-CVE-2026-66038.