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CVE-2026-66037 FFmpeg CVE debrief

CVE-2026-66037 is an uncontrolled resource consumption vulnerability in the IAMF demuxer of FFmpeg. The vulnerability allows an unauthenticated attacker to cause multi-gigabyte memory allocation from a 17-byte input file by supplying a crafted count_label field. The mix_presentation_obu() function in libavformat/iamf_parse.c calls av_calloc(count_label, sizeof(*language_label)) with an attacker-controlled value before validating available OBU data, enabling an allocation amplification of approximately 126 million bytes per input byte that exhausts process memory or triggers an OOM-kill during format probing. Users of FFmpeg through version 8.1.2 should be aware of this vulnerability and take steps to mitigate it.

Vendor
FFmpeg
Product
Unknown
CVSS
HIGH 7.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-24
Original CVE updated
2026-08-07
Advisory published
2026-07-24
Advisory updated
2026-08-07

Who should care

Users of FFmpeg through version 8.1.2, security teams, and operators should be aware of this vulnerability and take steps to mitigate it. This includes updating to a version of FFmpeg that includes the fix, such as the commit 5d7112c, and monitoring their systems for potential attacks.

Technical summary

The vulnerability is caused by the mix_presentation_obu() function in libavformat/iamf_parse.c, which calls av_calloc(count_label, sizeof(*language_label)) with an attacker-controlled value before validating available OBU data. This allows an attacker to cause multi-gigabyte memory allocation from a 17-byte input file, leading to potential denial-of-service attacks. The issue is fixed in commit 5d7112c. Users should update to a version of FFmpeg that includes this fix.

Defensive priority

High

Recommended defensive actions

  • Update FFmpeg to a version that includes the fix, such as the commit 5d7112c.
  • Monitor systems for potential attacks.
  • Implement compensating controls, such as limiting the size of input files.
  • Perform inventory checks to ensure that all systems using FFmpeg are updated and patched.
  • Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The CVE record was published on 2026-07-24T20:18:20.573Z and was last modified on 2026-07-27T20:34:24.887Z. The NVD entry is currently Awaiting Analysis. The vulnerability has a CVSS score of 7.1 and a severity of HIGH. Evidence is limited, and defenders should verify the affected scope and vendor guidance.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-66037 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-66037

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-66037 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-66037

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.