FFmpeg up to 8.x Native TIFF Decoder libavcodec/tiff.c tiff_unpack_zlib missing initialization

Summaryinfo

A vulnerability described as problematic has been identified in FFmpeg up to 8.x. This impacts the function tiff_unpack_zlib of the file libavcodec/tiff.c of the component Native TIFF Decoder. Such manipulation leads to missing initialization. This vulnerability is documented as CVE-2026-70631. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in FFmpeg up to 8.x. It has been rated as problematic. Affected by this issue is the function tiff_unpack_zlib of the file libavcodec/tiff.c of the component Native TIFF Decoder. The manipulation with an unknown input leads to a missing initialization vulnerability. Using CWE to declare the problem leads to CWE-456. The product does not initialize critical variables, which causes the execution environment to use unexpected values. Impacted is confidentiality. CVE summarizes:

FFmpeg versions from 0.5 up to, but not including, 9.0 contain an uninitialized heap memory disclosure vulnerability in the native TIFF decoder in libavcodec/tiff.c. An attacker who can cause FFmpeg to decode a crafted TIFF file can supply a valid Deflate-compressed strip that terminates successfully after producing fewer bytes than the declared strip requires. The tiff_unpack_zlib() function allocates a heap buffer sized for the full declared strip but copies all declared rows via memcpy() regardless of how many bytes zlib actually decompressed, causing unwritten bytes that can contain stale data from prior heap allocations to be incorporated into decoded image output and potentially exposing sensitive data in persistent services.

The advisory is available at code.ffmpeg.org. This vulnerability is handled as CVE-2026-70631 since 08/04/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit.

Upgrading to version 9.0 eliminates this vulnerability.

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Productinfo

Type

• Multimedia Processing Software

Name

• FFmpeg

Version

• 8.x

License

• open-source

Website

• Product: https://ffmpeg.org/

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