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CVE-2026-66038

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

High7.1EPSS 0.24%
Published
Updated
Reserved
Assigned by
VulnCheck

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.

Scores

CVSS scores of CVE-2026-66038, by who scored it
Scored byCVSSScoreVector
VulnCheckCNA (assigner)4.0High7.1CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
VulnCheckCNA (assigner)3.1Medium6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
NVDNVD · Analyzed4.0High7.1CVSS: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
EPSS (exploitation in 30 days)
0.24% · top 85% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.1.

Weakness

Affected products

  • FFmpeg · FFmpeg

    • affected ≤ 8.1.2
    • unaffected 86708357d126af84c16f80d9c57335d1e8c845c5

References (3)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .