CVE-2026-120243 FFmpeg CVE debrief

Who should care

Defenders responsible for systems using FFmpeg for video decoding, especially in environments where input streams may be untrusted or partially trusted, should assess potential exposure and impact.

Why it matters

Defenders should care about CVE-2026-120243 because it allows attackers to leak stack memory in FFmpeg 2.0 through 9.0.2, potentially leading to information disclosure. Roles responsible for system security, video decoding, and FFmpeg maintenance should assess exposure, especially in environments with untrusted input streams. The vulnerability's impact is moderate, and remediation involves updating FFmpeg versions. Evidence is limited, and further verification is required to determine the full scope of affected systems and potential consequences.

• Potential information disclosure through stack memory leakage
• Possible exposure of sensitive data or code execution context
• Requires verification of FFmpeg versions and exposure in specific environments
• Remediation priority is moderate due to the limited scope of exploitation

Technical summary

The vulnerability is caused by the use of uninitialized variables in the Go2Meeting decoder, specifically in the kempf_restore_buf() function. This allows attackers to leak stack memory, including pointers or stack guards, into decoded output. The vulnerability affects FFmpeg versions 2.0 through 9.0.2 and has a moderate impact. Defenders should prioritize verifying exposure and assessing potential impact, especially in environments using FFmpeg for video decoding. Evidence is limited, and further verification is required to determine the full scope of affected systems and potential consequences.

Defensive priority

Defenders should prioritize verifying exposure and assessing potential impact, especially in environments using FFmpeg for video decoding.

Recommended defensive actions

• Verify FFmpeg versions 2.0 through 9.0.2 are in use and assess potential exposure
• Review and update FFmpeg to a version beyond 9.0.2 if possible
• Monitor for and restrict suspicious G2M3/G2M4 stream inputs
• Implement additional memory safety controls around FFmpeg usage
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The vulnerability is caused by the use of uninitialized variables in the Go2Meeting decoder, specifically in the kempf_restore_buf() function. This allows attackers to leak stack memory, including pointers or stack guards, into decoded output.

Sources and 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.