What’s Vulnerable › Vulnerabilities

CVE-2026-70631: FFmpeg 0.5 < 9.0 Uninitialized Heap Memory Read in TIFF Decoder

• Severity: medium (CVSS 5.5 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: 2026-08-06 · updated 2026-09-01
• Weakness: CWE-908

Description

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.

Affected products

• FFmpeg: from 0.5 before 9 — fixed in 9

How to fix

Upgrade to a fixed version: FFmpeg 9. Check the vendor advisory for mitigations.

References

• https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/2f234ea34c81288e3840fca632dd16481d8de39f
• https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/3c287af3affe1286350faa69c02bcc5d49de18bb
• https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/a991b1fecbd8c9e6f4fc31c191bd12e4be27dbf7
• https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23899
• https://www.vulncheck.com/advisories/ffmpeg-uninitialized-heap-memory-read-in-tiff-decoder

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