Vulnerability record · CVE-2026-66038 · published 24 July 2026

CVE-2026-66038: Ffmpeg use of uninitialized resource vulnerability

Ffmpeg · Ffmpeg

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.

7.1 CVSS 4.0 High EPSS 0.44% · top 64.3% CWE-908 · Use of uninitialized resource

7.1CVSS 4.0 base score

0.44%EPSS exploitation probability, 30 days

NoNot in CISA KEV

1Affected product versions listed by NVD

3References

7 Aug 2026Last modified by NVD

Description

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

Ffmpeg Ffmpeg

References

Link	Tags
https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/e7cbfd1c507b57a806a5825b87d609963e862c8c	Patch
https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23626	Issue TrackingPatch
https://www.vulncheck.com/advisories/ffmpeg-lcl-zlib-video-decoder-information-disclosure-via-lcldec-c	Third Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2013-0864Ffmpeg vulnerabilityThe gif_copy_img_rect function in libavcodec/gifdec.c in FFmpeg before 1.1.2 performs an incorrect calculation for an "end pointer," which allows rem…EPSS 2.8%23 Nov 2013 10.0CVE-2013-0872Ffmpeg memory buffer overflow vulnerabilityThe swr_init function in libswresample/swresample.c in FFmpeg before 1.1.3 allows remote attackers to have an unspecified impact via an invalid or un…EPSS 2.8%23 Nov 2013 10.0CVE-2013-0873Ffmpeg improper input validation vulnerabilityThe read_header function in libavcodec/shorten.c in FFmpeg before 1.1.3 allows remote attackers to have an unspecified impact via an invalid channel …EPSS 2.8%23 Nov 2013 10.0CVE-2013-4265Ffmpeg vulnerabilityThe av_reallocp_array function in libavutil/mem.c in FFmpeg before 2.0.1 has an unspecified impact and remote vectors related to a "wrong return code…EPSS 2.5%23 Nov 2013 10.0CVE-2011-3937Ffmpeg vulnerabilityThe H.263 codec (libavcodec/h263dec.c) in FFmpeg 0.7.x before 0.7.12, 0.8.x before 0.8.11, and unspecified versions before 0.10, and in Libav 0.5.x b…EPSS 2.3%5 Jan 2013 10.0CVE-2012-2797Ffmpeg vulnerabilityUnspecified vulnerability in the decode_frame_mp3on4 function in libavcodec/mpegaudiodec.c in FFmpeg before 0.11 and Libav 0.8.x before 0.8.5 has unk…EPSS 2.6%10 Sep 2012 10.0CVE-2012-2798Libav vulnerabilityUnspecified vulnerability in the decode_dds1 function in libavcodec/dfa.c in FFmpeg before 0.11, and Libav 0.7.x before 0.7.7 and 0.8.x before 0.8.4,…EPSS 2.9%10 Sep 2012 10.0CVE-2012-2799Ffmpeg vulnerabilityUnspecified vulnerability in libavcodec/wmalosslessdec.c in FFmpeg before 0.11 has unknown impact and attack vectors, related to the "put bit buffer …EPSS 2.5%10 Sep 2012

Source: NIST National Vulnerability Database (record CVE-2026-66038), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.