Vulnerability in Ffmpeg
CVE-2026-70631
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.002 (7.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 7.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- Ffmpeg — versions 0.5
Weakness classification (CWE)
References
- code.ffmpeg.org/FFmpeg/FFmpeg/commit/2f234ea34c81288e3840fca632dd16481d8de39f (Patch, patch)
- code.ffmpeg.org/FFmpeg/FFmpeg/commit/3c287af3affe1286350faa69c02bcc5d49de18bb (Patch, patch)
- code.ffmpeg.org/FFmpeg/FFmpeg/commit/a991b1fecbd8c9e6f4fc31c191bd12e4be27dbf7 (related, Patch)
- code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23899 (issue-tracking, Patch, Issue Tracking)
- www.vulncheck.com/advisories/ffmpeg-uninitialized-heap-memory-read-in-tiff-deco… (Patch, Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-70631?
- CVE-2026-70631 is a medium-severity vulnerability in Ffmpeg, classified under Use of Uninitialized Resource. CVSS score: 5.5/10. Published 2026-08-06.
- How severe is CVE-2026-70631?
- Medium severity. CVSS v3 base score is 5.5 out of 10.