# CVE-2026-125182: FFmpeg through 9.0.2 Out-of-Bounds Read via Cook Decoder js_subband_start

Status: published. Published: 2026-11-09. Updated: 2026-11-13.

FFmpeg through 9.0.2 contains an out-of-bounds read vulnerability in the Cook decoder joint_decode() function because cook_decode_init() does not check js_subband_start against subbands. Attackers can supply a crafted RealMedia file whose extradata causes reads past decode_buffer_0, leaking pointers and decoder state into decoded audio to help defeat ASLR.

## 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/7145d13201c9f9c5253f40295714faa4f4ada1a0

## Affected products and versions

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

## Severity and prioritization

- CVSS 4.0: 4.8 (medium); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 3.3 (low); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N; source: CNA: VulnCheck

- CVSS 4.0: 4.8 (medium); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/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: 3.3 (low); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.13% as of 2026-11-12; percentile 2.54%

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

- Weaknesses: CWE-125

## Exploit evidence

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

## References

- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24763 (CNA: VulnCheck; issue-tracking)

- https://github.com/FFmpeg/FFmpeg/commit/7145d13201c9f9c5253f40295714faa4f4ada1a0 (CNA: VulnCheck; patch)

- https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/cook.c#L854 (CNA: VulnCheck; technical-description)

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

- https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-out-of-bounds-read-via-cook-decoder-js-subband-start (CNA: VulnCheck; third-party-advisory)

- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24763 (disclosure@vulncheck.com)

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

- https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/cook.c#L854 (disclosure@vulncheck.com)

- https://github.com/FFmpeg/FFmpeg/commit/7145d13201c9f9c5253f40295714faa4f4ada1a0 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-out-of-bounds-read-via-cook-decoder-js-subband-start (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-125182; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-125182; retrieved 2026-11-11; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-125182; retrieved 2026-11-13; source updated Not reported

Revision: 468344d46d20d4bedb1ff8a04ce8acc5e932d41011e5ff13a58a3972c5d6d1b0

Canonical: https://y2.dev/cve/CVE-2026-125182

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