CVE-2026-125257 PUBLISHED

FFmpeg through 9.0.2 Heap Overflow via Nellymoser Encoder Trellis Search

Assigner: VulnCheck
Reserved: 09.11.2026 Published: 09.11.2026 Updated: 09.11.2026

FFmpeg through 9.0.2 contains an off-by-one heap overflow vulnerability in get_exponent_dynamic() in libavcodec/nellymoserenc.c that allows writing one element past the opt and path allocations. Attackers can supply crafted audio to applications encoding Nellymoser with trellis enabled, causing idx to equal OPT_SIZE and overwrite adjacent heap memory.

CVSS Vector: 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
CVSS Score: 7.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Local	Confidentiality	High	Confidentiality	None
Attack Complexity	High	Integrity	High	Integrity	None
Attack Requirements	Present	Availability	High	Availability	None
Privileges Required	None
User Interaction	Passive

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS Score: 7

Attack Vector	Local	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	High
User Interaction	Required	Availability Impact	High

CVSS 3.1

Product Status

Vendor	FFmpeg
Product	FFmpeg
Versions	Default: unaffected affected from 0 to 9.0.2 (incl.)

CVE-2026-125257 PUBLISHED

FFmpeg through 9.0.2 Heap Overflow via Nellymoser Encoder Trellis Search

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Problem Types