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Fencer Vulns
medium 6.5

CVE-2026-66038 json

FFmpeg LCL/ZLIB Video Decoder Information Disclosure via lcldec.c

published 2026-07-24 3 mo ago modified 2026-08-08 3 mo ago also EUVD-2026-48740 , GHSA-8mx4-8xfc-qr43 , JLSEC-2026-1184

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 15%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia FFMPEG_jll 9.0.0+0
  • julia FFMPEG_nogpl_jll 9.0.0+0
  • julia FFplay_jll 9.0.0+0
  • ffmpeg Debian 14 7:9.0.2-1

debian advisories DEBIAN-CVE-2026-66038

  • ffmpeg Ubuntu Pro 16.04 LTS 7:2.8.17-0ubuntu0.1+esm15
  • ffmpeg Ubuntu Pro 18.04 LTS 7:3.4.11-0ubuntu0.1+esm13
  • ffmpeg Ubuntu Pro 20.04 LTS 7:4.2.7-0ubuntu0.1+esm14
  • ffmpeg Ubuntu Pro 22.04 LTS 7:4.4.2-0ubuntu0.22.04.1+esm13
  • ffmpeg Ubuntu Pro 24.04 LTS 7:6.1.1-3ubuntu5+esm11
  • ffmpeg Ubuntu Pro 26.04 LTS 7:8.0.1-3ubuntu2+esm3

ubuntu advisories UBUNTU-CVE-2026-66038

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • ffmpeg-7 SLES 16.0, SLES for SAP applications 16.0 7.1.4-160000.3.1
  • ffmpeg-4 SLE Workstation Extension 15 SP7, SLE Module for Package Hub 15 SP7 4.4.8-150600.13.52.1
  • ffmpeg-4 SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE High Performance Computing 15 SP4-LTSS +1 more 4.4.8-150400.3.72.1

suse advisories SUSE-SU-2026:23222-1SUSE-SU-2026:23232-1SUSE-SU-2026:3542-1SUSE-SU-2026:3529-1

  • ffmpeg-7 openSUSE Tumbleweed 7.1.5-2.1
  • ffmpeg-7 openSUSE Leap 16.0 7.1.4-160000.3.1
  • ffmpeg-4 openSUSE Tumbleweed 4.4.8-3.1
  • ffmpeg-4 openSUSE Leap 16.0 4.4.7-bp160.3.1

opensuse advisories openSUSE-SU-2026:11665-1openSUSE-SU-2026:21572-1openSUSE-SU-2026:11448-1openSUSE-SU-2026:21522-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-66038 updated cvss 6.5

FFmpeg: Information disclosure via malformed zlib video stream

  • Red Hat Enterprise Linux AI (RHEL AI) 3 ffmpeg, rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9, +1 more
    affected: workaround, no fix available
  • Red Hat OpenShift AI 3.3 rhoai/odh-vllm-gaudi-rhel9 1789121263
    fixed: vendor fix RHSA-2026:73987
  • Red Hat OpenShift AI 3.3 rhoai/odh-cli-rhel9 1790070206, rhoai/rhai-cli-rhel9 1790070206, rhoai/odh-mlflow-rhel9 1789653606, rhoai/odh-trainer-rhel9 1790136369, rhoai/odh-maas-api-rhel9 1790131842, rhoai/odh-mlserver-rhel9 1789121365, +76 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 7.1 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
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
CNA 4.0 7.1 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:X/V:X/RE:X/U:X
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
OSV 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
julia FFMPEG_jll
<9.0.0+0
9.0.0+0
julia FFMPEG_nogpl_jll
<9.0.0+0
9.0.0+0
julia FFplay_jll
<9.0.0+0
9.0.0+0

Affected products

  • FFmpeg FFmpeg

Classification

Weakness
  • CWE-908 Use of Uninitialized Resource

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.