CVE-2026-66038: Ffmpeg

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Ffmpeg Ffmpeg: up to and including 8.1.2

Published 2026-07-24. Last modified 2026-08-07.