CVE-2026-66038

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory (severity: HIGH) published 2026-07-24. the CNA's CVSS baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Trending — 4 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.5
EG Score
6.5(high)
EG Risk
29(Track)
EG Risk 29/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
17%
KEV
Not listed

Published

July 24, 2026

Last Modified

July 28, 2026

Advisory Details (3)

Auto-updated Jul 25, 2026
No patch confirmed yet.
generic

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

https://www.vulncheck.com/advisories/ffmpeg-lcl-zlib-video-decoder-information-disclosure-via-lcldec-c
generic

#23626 - avcodec/lcldec: zero the not-decoded tail to avoid heap disclosure - FFmpeg/FFmpeg - FFmpeg Forgejo

https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23626
generic

avcodec/lcldec: zero the not-decoded tail to avoid heap disclosure · e7cbfd1c50 - FFmpeg/FFmpeg - FFmpeg Forgejo

https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/e7cbfd1c507b57a806a5825b87d609963e862c8c

Vendor Advisories for CVE-2026-66038(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 15× in last 7d / 15× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-28 01:30 UTCEG score recompute
  2. 2026-07-28 01:30 UTCGHSA enrichment
  3. 2026-07-27 20:43 UTCEG score recompute
  4. 2026-07-27 20:43 UTCGHSA enrichment
  5. 2026-07-27 14:14 UTCEPSS rescore
  6. 2026-07-27 05:28 UTCEG score recompute
  7. 2026-07-27 05:28 UTCGHSA enrichment
  8. 2026-07-26 14:54 UTCEPSS rescore
  9. 2026-07-26 14:54 UTCEPSS rescore
  10. 2026-07-26 02:55 UTCEG score recompute
  11. 2026-07-26 02:55 UTCGHSA enrichment
  12. 2026-07-25 14:18 UTCEPSS rescore
  13. 2026-07-25 14:18 UTCEPSS rescore
  14. 2026-07-24 20:12 UTCEG score recompute
  15. 2026-07-24 20:12 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-66038?
CVE-2026-66038 is a medium vulnerability published on July 24, 2026. 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()…
When was CVE-2026-66038 disclosed?
CVE-2026-66038 was first published in the National Vulnerability Database on July 24, 2026, with the most recent update on July 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66038 actively exploited?
CVE-2026-66038 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 82.8% of all scored CVEs.
What is the CVSS score of CVE-2026-66038?
CVE-2026-66038 has a CVSS v4.0 base score of 6.5 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-66038?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66038, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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