FFmpeg through 9.0.2 Uninitialized Heap Disclosure via MLZ Decompressor in ALS Decoder
Summary
| CVE | CVE-2026-125103 |
|---|---|
| State | PUBLISHED |
| Assigner | VulnCheck |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-09 19:16:51 UTC |
| Updated | 2026-11-09 19:16:51 UTC |
| Description | FFmpeg through 9.0.2 contains an information disclosure vulnerability in ff_mlz_decompression() in libavcodec/mlz.c, which accepts string codes beyond the dictionary's next free code. Attackers can supply a crafted MPEG-4 ALS file with malformed initial or out-of-range codes to copy uninitialized heap bytes into decoded audio output. |
Risk And Classification
Primary CVSS: v4.0 4.8 MEDIUM from [email protected]
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
Problem Types: CWE-908 | CWE-908 Use of Uninitialized Resource
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 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/C... |
| 4.0 | CNA | CVSS | 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 |
| 3.1 | [email protected] | Primary | 3.3 | LOW | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N |
| 3.1 | CNA | CVSS | 3.3 | LOW | CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N |
CVSS v4.0 Breakdown
Attack Vector
LocalAttack Complexity
LowAttack Requirements
NonePrivileges Required
NoneUser Interaction
PassiveConfidentiality
LowIntegrity
NoneAvailability
NoneSub Conf.
NoneSub Integrity
NoneSub Availability
NoneCVSS: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
CVSS v3.1 Breakdown
Attack Vector
LocalAttack Complexity
LowPrivileges Required
NoneUser Interaction
RequiredScope
UnchangedConfidentiality
LowIntegrity
NoneAvailability
NoneCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uninitialized-heap-disclosure... | [email protected] | www.vulncheck.com | |
| github.com/FFmpeg/FFmpeg | [email protected] | github.com | |
| github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/mlz.c | [email protected] | github.com | |
| code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25703 | [email protected] | code.ffmpeg.org | |
| github.com/FFmpeg/FFmpeg/commit/db98784a72600a94f7ebd5f016a37e01a505c27b | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Joshua Rogers (AISLE Research) (en)
CNA: Michael Niedermayer (en)
There are currently no legacy QID mappings associated with this CVE.