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CVE-2026-66039: Ffmpeg Heap Buffer Overflow (CVSS 8.7)

CVE-2026-66039 is a high severity heap buffer overflow in Ffmpeg with a CVSS score of 8.7. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Last updated: Aug 7, 2026

Quick answer

Direct answer

CVE-2026-66039 is a high severity heap buffer overflow in Ffmpeg with a CVSS score of 8.7. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Risk scores

CVSS base score
8.7HIGH
EPSS probability
0.31%
Higher than 22 percent of all CVEs
CISA KEV
Not listed
CVSS metricWhat it means
Attack vector (AV:N)Network: reachable remotely
Attack complexity (AC:L)Low complexity
Attack requirements (AT:N)No attack requirements
Privileges required (PR:N)No privileges required
User interaction (UI:P)Passive user interaction
Confidentiality (VC:H)High confidentiality impact
Integrity (VI:H)High integrity impact
Availability (VA:H)High availability impact

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/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

About Ffmpeg

CVE-2026-66039 affects Ffmpeg, a product from Ffmpeg. Before acting, confirm where Ffmpeg runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.

What the flaw is

In plain terms: FFmpeg through 8.1.2, fixed in commit aafb5c6, contains a signed integer overflow vulnerability in the MACE6 audio decoder that allows attackers to corrupt heap memory by supplying a crafted CAF file with a malicious bytes_per_packet value. Attackers can craft a CAF file with oversized bytes_per_packet and frames_per_packet values in the desc chunk to trigger an integer overflow in mace_decode_frame() during output sample count computation, resulting in an undersized buffer allocation and heap out-of-bounds write that could enable code execution.

The weakness class is Heap Buffer Overflow. A write past the end of a heap buffer corrupts nearby memory.

Based on its CVSS vector, the flaw can be reached over the network, needs no login, and relies on a user taking an action. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Affected versions and timeline

FieldDetail
ProductFfmpeg
Affected versionsFfmpeg up to and including 8.1.2
PublishedJul 24, 2026
Last modifiedAug 7, 2026
Added to CISA KEVNot listed
Assigning CNAdisclosure@vulncheck.com

How to detect it

  • Inventory every instance of Ffmpeg and record the running version against the affected range above.
  • Check external attack surface scans for internet facing instances of the component.
  • Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
  • Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.

How to fix it

  • Apply the fixed version of Ffmpeg named in the vendor advisory.
  • If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
  • Rescan after the change to prove the exposure is gone, then close the ticket.

CTEM action plan

CTEM stageWhat to do for this CVE
ScopeAdd every business service that depends on Ffmpeg to the current CTEM cycle.
DiscoverFind all instances, including shadow and cloud deployments, and record versions and exposure.
PrioritizeRank using EPSS and CVSS together with asset exposure and business impact.
ValidateConfirm the flaw is reachable and exploitable in your environment and that compensating controls work.
MobilizeAssign the fix to the asset owner with a due date matched to the priority, then verify closure.

CWE References

Technical References

Frequently asked questions

CVE-2026-66039 is a high severity heap buffer overflow in Ffmpeg with a CVSS score of 8.7. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Related CVEs

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