FFmpeg up to 8.1.2 LCL/ZLIB Video Decoder lcldec.c zlib_decomp information disclosure

Summaryinfo

A vulnerability was found in FFmpeg up to 8.1.2. It has been declared as problematic. This impacts the function zlib_decomp of the file lcldec.c of the component LCL/ZLIB Video Decoder. Such manipulation leads to information disclosure. This vulnerability is listed as CVE-2026-66038. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in FFmpeg up to 8.1.2 and classified as problematic. Affected by this issue is the function zlib_decomp of the file lcldec.c of the component LCL/ZLIB Video Decoder. The manipulation with an unknown input leads to a information disclosure vulnerability. Using CWE to declare the problem leads to CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Impacted is confidentiality. CVE summarizes:

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.

The advisory is available at code.ffmpeg.org. This vulnerability is handled as CVE-2026-66038 since 07/23/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1592 by the MITRE ATT&CK project.

Applying the patch 86708357d126af84c16f80d9c57335d1e8c845c5 is able to eliminate this problem.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Multimedia Processing Software

Name

• FFmpeg

Version

• 8.1.0
• 8.1.1
• 8.1.2

License

• open-source

Website

• Product: https://ffmpeg.org/

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