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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-66038
StatePUBLISHED
AssignerVulnCheck
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-24 20:18:20 UTC
Updated2026-07-24 21:16:46 UTC
DescriptionFFmpeg 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.

Risk And Classification

Primary CVSS: v4.0 7.1 HIGH from [email protected]

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

Problem Types: CWE-908 | CWE-908 Use of Uninitialized Resource

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7.1HIGHCVSS: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/C...
4.0CNACVSS7.1HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
3.1CNACVSS6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Passive
Confidentiality
High
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

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

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA FFmpeg FFmpeg affected 8.1.2 semver Not specified
CNA FFmpeg FFmpeg unaffected 86708357d126af84c16f80d9c57335d1e8c845c5 git Not specified

References

ReferenceSourceLinkTags
www.vulncheck.com/advisories/ffmpeg-lcl-zlib-video-decoder-information-disclosu... [email protected] www.vulncheck.com
code.ffmpeg.org/FFmpeg/FFmpeg/commit/e7cbfd1c507b57a806a5825b87d609963e862c8c [email protected] code.ffmpeg.org
code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23626 [email protected] code.ffmpeg.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Adrian Junge (vurlo) (en)

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