VDB-433251 · CVE-2026-125103 · GCVE-0-2026-125103

FFmpeg up to 9.0.2 MLZ Decompression libavcodec/mlz.c ff_mlz_decompression uninitialized variable

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
3.0	$0-$5k	0.00+

Summaryinfo

A vulnerability was found in FFmpeg up to 9.0.2. It has been rated as problematic. Impacted is the function ff_mlz_decompression of the file libavcodec/mlz.c of the component MLZ Decompression. Performing a manipulation results in uninitialized variable. This vulnerability is identified as CVE-2026-125103. The attack is only possible with local access. There is not any exploit available.

Detailsinfo

A vulnerability classified as problematic has been found in FFmpeg up to 9.0.2. This affects the function ff_mlz_decompression of the file libavcodec/mlz.c of the component MLZ Decompression. The manipulation with an unknown input leads to a uninitialized variable vulnerability. CWE is classifying the issue as CWE-457. The code uses a variable that has not been initialized, leading to unpredictable or unintended results. This is going to have an impact on confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at code.ffmpeg.org. This vulnerability is uniquely identified as CVE-2026-125103 since 11/09/2026. The exploitability is told to be easy. Attacking locally is a requirement. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

Multimedia Processing Software

Name

FFmpeg

Version

License

open-source

Website

Product: https://ffmpeg.org/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 3.0
VulDB Meta Temp Score: 3.0

VulDB Base Score: 2.8
VulDB Temp Score: 2.8
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 3.3
CNA Vector (VulnCheck): 🔒

CVSSv2info

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Uninitialized variable
CWE: CWE-457 / CWE-453
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

11/09/2026 Advisory disclosed
11/09/2026 +0 days CVE reserved
11/09/2026 +0 days VulDB entry created
11/09/2026 +0 days VulDB entry last update

Sourcesinfo

Product: ffmpeg.org

Advisory: code.ffmpeg.org
Status: Not defined

CNA: VulnCheck
CVE: CVE-2026-125103 (🔒)

GCVE (CVE): GCVE-0-2026-125103
GCVE (VulDB): GCVE-100-433251

Entryinfo

Created: 11/09/2026 20:23
Changes: 11/09/2026 20:23 (75)
Complete: 🔍
Cache ID: 216::103