CVE-2026-125269
Received Received - Intake

Double Free in FFmpeg via H.264 SEI Message Handling

Publication date: 2026-11-09

Last updated on: 2026-11-09

Assigner: VulnCheck

Description
FFmpeg through 9.0.2 contains a double free vulnerability in libavcodec/cbs_sei.c where cbs_sei_delete_message() leaves a stale extension_data reference that ff_cbs_sei_add_message() reuses. Attackers can supply a crafted H.264 stream with a display orientation SEI message followed by payload extension data, processed by h264_metadata with display_orientation=insert, to corrupt heap memory.

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Meta Information

Published
2026-11-09
Last Modified
2026-11-09
Generated
2026-11-10
AI Q&A
2026-11-09
EPSS Evaluated
N/A
NVD
CVE-2026-125269
EUVD
EUVD-2026-120219

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
FFmpeg FFmpeg From 0 (inc) to 9.0.2 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-415 The product calls free() twice on the same memory address.

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Executive Summary

This vulnerability is a double free issue in FFmpeg 9.0.2 within libavcodec/cbs_sei.c. The function cbs_sei_delete_message() fails to clear an extension_data reference, which is then reused by ff_cbs_sei_add_message(). Attackers can exploit this by sending a crafted H.264 stream with a display orientation SEI message followed by payload extension data. When processed by h264_metadata with display_orientation=insert, it corrupts heap memory.

Detection Guidance

This vulnerability involves a double free in FFmpeg's libavcodec/cbs_sei.c when processing H.264 streams with specific SEI messages. Detection requires analyzing FFmpeg versions and processing crafted streams. No direct detection commands are provided in the context.

Impact Analysis

This vulnerability could allow attackers to execute arbitrary code or cause denial of service on systems using vulnerable FFmpeg versions. It may lead to crashes, data corruption, or unauthorized access if exploited via malicious media files.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling heap memory corruption through crafted H.264 streams. Exploitation may lead to unauthorized data access, integrity breaches, or service disruption in systems processing sensitive media data, which are critical concerns under these regulations.

Mitigation Strategies

Upgrade FFmpeg to a patched version beyond 9.0.2. Avoid processing untrusted H.264 streams with display_orientation=insert in h264_metadata. Monitor for crashes or memory corruption when handling SEI messages.

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