Vulnerability · Published Jul 24, 2026 · Assigned by VulnCheck
CVE-2026-66038FFmpeg LCL/ZLIB Video Decoder Information Disclosure via lcldec.c
Medium 6.5
In plain English
A medium-severity security flaw in FFmpeg from FFmpeg. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | ffmpeg | no fix listed | DEBIAN-CVE-2026-66038 |
| Debian:13 | ffmpeg | no fix listed | DEBIAN-CVE-2026-66038 |
| Debian:14 | ffmpeg | 7:9.0.2-1 | DEBIAN-CVE-2026-66038 |
| Ubuntu:26.10 | ffmpeg | no fix listed | UBUNTU-CVE-2026-66038 |
Affected products (as reported)
Weakness: CWE-908 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
References
- Pull Request issue-tracking
- Patch Commit patch
- https://www.vulncheck.com/advisories/ffmpeg-lcl-zlib-video-decoder-information-disclosure-via-lcldec-c third-party-advisory