# CVE-2026-125233: FFmpeg through 9.0.2 Heap Buffer Overflow via DVB Subtitle Encoder

Status: published. Published: 2026-11-09. Updated: 2026-11-14.

FFmpeg through 9.0.2 contains a heap buffer overflow vulnerability in dvbsub_encode() in libavcodec/dvbsubenc.c that undercounts each CLUT segment header by two bytes. Attackers can supply a file with many bitmap subtitle rectangles that, when transcoded to the dvbsub encoder, writes past the output buffer and corrupts heap memory.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/FFmpeg/FFmpeg/commit/7f80b2ad83f37a4998d9617495c92b28a7339a90

## Affected products and versions

- FFmpeg / FFmpeg (ffmpeg/ffmpeg): ≥ 0; ≤ 9.0.2 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.5 (high); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: CNA: VulnCheck

- CVSS 4.0: 8.5 (high); CVSS:4.0/AV:L/AC:L/AT:N/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.14% as of 2026-11-13; percentile 3.50%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-131

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24913 (CNA: VulnCheck; issue-tracking)

- https://github.com/FFmpeg/FFmpeg/commit/7f80b2ad83f37a4998d9617495c92b28a7339a90 (CNA: VulnCheck; patch)

- https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/dvbsubenc.c#L363 (CNA: VulnCheck; technical-description)

- https://github.com/FFmpeg/FFmpeg (CNA: VulnCheck; product)

- https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-heap-buffer-overflow-via-dvb-subtitle-encoder (CNA: VulnCheck; third-party-advisory)

- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24913 (disclosure@vulncheck.com)

- https://github.com/FFmpeg/FFmpeg (disclosure@vulncheck.com)

- https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/dvbsubenc.c#L363 (disclosure@vulncheck.com)

- https://github.com/FFmpeg/FFmpeg/commit/7f80b2ad83f37a4998d9617495c92b28a7339a90 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-heap-buffer-overflow-via-dvb-subtitle-encoder (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-125233; retrieved 2026-11-14; source updated 2026-11-14

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-125233; retrieved 2026-11-11; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-125233; retrieved 2026-11-14; source updated Not reported

Revision: 36223986420161151617058931c7ef144ad32f5abd7022553d067674e41f0353

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