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

CVE ID :CVE-2026-66038

Published : July 24, 2026, 8:18 p.m. | 1 hour, 32 minutes ago

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.

Severity: 7.1 | HIGH

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