CVE-2026-66038Network attack vector

Heap disclosure via short LCL/ZLIB decompression

Published Jul 24, 2026 · Updated Jul 24, 2026

Information disclosure in FFmpeg 8.1.2 and earlier allows remote attackers to expose heap memory via crafted LCL/ZLIB video streams. The zlib_decomp() function in libavcodec/lcldec.c accepts a stream that inflates short, then RGB24 conversion copies full-size rows from the partially initialized allocation into an AVFrame. Disclosure requires decoded output to reach an attacker-observable endpoint; affected pipelines expose stale allocator data, including pointer-derived bytes, but do not alter data or interrupt service.

CVSS severity7.1
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in FFmpeg 8.1.2 and earlier allows remote attackers to expose heap memory via crafted LCL/ZLIB video streams. The zlib_decomp() function in libavcodec/lcldec.c accepts a stream that inflates short, then RGB24 conversion copies full-size rows from the partially initialized allocation into an AVFrame. Disclosure requires decoded output to reach an attacker-observable endpoint; affected pipelines expose stale allocator data, including pointer-derived bytes, but do not alter data or interrupt service.

The record

CVE
CVE-2026-66038
Published
Jul 24, 2026
Updated
Jul 24, 2026
Vendor
FFmpeg
Product
FFmpeg
Classifications
CWE-908
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=8.1.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FFmpeg · FFmpegversion=0 <=8.1.2

Published CVSS scores

6.5Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
7.1VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
6.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
6.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-908Use of Uninitialized Resource

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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