CVE-2026-64830: FFmpeg 2.1 - 8.1.2 Heap Buffer Overflow via VobSub Subtitle Demuxer

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.6%

EPSS score, percentile 50.9 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

8.7 High

CVSS v4.0 base score, given by the CNA

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (1)

Which versions are affected?

Affected

• 2.1 through 8.1.2

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

• Patch Commit (Patch)

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Versions not listed are: affected.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

FFmpeg versions 2.1 through 8.1.2 contains a heap buffer overflow vulnerability in the VobSub subtitle demuxer that allows attackers to corrupt adjacent heap memory by supplying a malicious .sub/.idx subtitle file declaring more distinct stream IDs than the fixed-size array bounds in libavformat/mpeg.c. Attackers can craft a subtitle file with excessive distinct stream IDs to trigger unbounded wr…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-64830 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 22 Jul 2026.
• The CVE record carries a CVSS v4.0 base score of 8.7 (High), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.6% (percentile 50.9), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact total.
• The credits in the CVE record name AISLE as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

FFmpeg 2.1 - 8.1.2 Heap Buffer Overflow via VobSub Subtitle Demuxer

FFmpeg versions 2.1 through 8.1.2 contains a heap buffer overflow vulnerability in the VobSub subtitle demuxer that allows attackers to corrupt adjacent heap memory by supplying a malicious .sub/.idx subtitle file declaring more distinct stream IDs than the fixed-size array bounds in libavformat/mpeg.c. Attackers can craft a subtitle file with excessive distinct stream IDs to trigger unbounded writes beyond the vobsub->q[] array boundary via ff_subtitles_queue_insert(), potentially achieving arbitrary code execution in any application using FFmpeg's VobSub demuxer.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline