Sources: National Vulnerability Database, CVE.org, CISA KEV, FIRST EPSS
CVE-2026-125269 Overview
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.
Critical Impact
Affected Products
- FFmpeg: see the vendor advisory for the exact affected versions
Discovery Timeline
- 2026-11-09: CVE-2026-125269 published to the National Vulnerability Database by disclosure@vulncheck.com
- 2026-11-09: last updated in the NVD database
Technical Details for CVE-2026-125269
Vulnerability Analysis
CVE-2026-125269 is a Security Vulnerability weakness (CWE-415) in FFmpeg. Based on its CVSS vector, the flaw needs local or adjacent access, needs no login, and relies on a user taking an action.
With a CVSS base score of 7.3, apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Root Cause
The vendor description states: 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.
Attack Vector
Based on the CVSS vector, the flaw needs local or adjacent access, needs no login, and relies on a user taking an action. Attack complexity is high complexity.
No exploitation in the wild is confirmed by CISA at the time of the last update. Check the references below for any vendor or researcher proof of concept.
CVSS:4.0/AV:L/AC:H/AT:P/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
Detection Methods for CVE-2026-125269
Detection Strategies
- Inventory every instance of FFmpeg and compare the running version with the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Run an authenticated vulnerability scan once your scanner ships a check for this CVE.
Monitoring Recommendations
- Forward FFmpeg application, access and audit logs to your SIEM for retrospective hunting.
- Alert on new processes, configuration changes or outbound connections from the affected service.
- Track the vendor advisory and the CISA KEV catalog for changes in exploitation status.
How to Mitigate CVE-2026-125269
Immediate Actions Required
- Apply the fixed version of FFmpeg named in the vendor advisory.
- Prioritize internet facing and business critical instances first.
- Rescan after the change to confirm the exposure is closed.
Patch Information
Use the fixed version listed in the vendor advisory for FFmpeg.
Workarounds
- If patching must wait, restrict network access to the affected service and place it behind authentication or a web application firewall rule.
CWE References
Technical References
This entry is built directly from NVD, CISA KEV and EPSS data. Verify fixed versions in the vendor advisory before you deploy.
Frequently asked questions
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