What’s Vulnerable › Vulnerabilities

CVE-2026-66038: FFmpeg LCL/ZLIB Video Decoder Information Disclosure via lcldec.c

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-24 · updated 2026-08-07
• Weakness: CWE-908

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.

Affected products

• FFmpeg: through 8.1.2

References

• https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/e7cbfd1c507b57a806a5825b87d609963e862c8c
• https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23626
• https://www.vulncheck.com/advisories/ffmpeg-lcl-zlib-video-decoder-information-disclosure-via-lcldec-c

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