CVE-2026-66038

NameCVE-2026-66038
DescriptionFFmpeg 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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
ffmpeg (PTS)bullseye7:4.3.7-0+deb11u1vulnerable
bullseye (security)7:4.3.9-0+deb11u2vulnerable
bookworm, bookworm (security)7:5.1.9-0+deb12u1vulnerable
trixie (security), trixie7:7.1.5-0+deb13u1vulnerable
forky, sid7:8.1.2-2vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
ffmpegsource(unstable)(unfixed)

Notes

https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23626
https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/e7cbfd1c507b57a806a5825b87d609963e862c8c

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