Mozilla Firefox up to 140.16/153.3/156 Gtk use after free

CVSS Meta Temp Score
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Current Exploit Price (≈)
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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.
7.8$5k-$25k1.11-

Summaryinfo

A vulnerability classified as critical was found in Mozilla Firefox up to 140.16/153.3/156. Affected by this issue is some unknown functionality of the component Gtk. The manipulation results in use after free. This vulnerability is known as CVE-2026-100818. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as critical has been found in Mozilla Firefox up to 140.16/153.3/156. Affected is an unknown function of the component Gtk. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Sandbox escape due to use-after-free in the Widget: Gtk component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17.

The advisory is available at bugzilla.mozilla.org. This vulnerability is traded as CVE-2026-100818 since 09/26/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 09/29/2026).

Upgrading to version 140.17, 153.4 or 157 eliminates this vulnerability.

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Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.9
VulDB Meta Temp Score: 7.8

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

ADP CISA Base Score: 9.6
ADP CISA Vector: 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

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

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Firefox 140.17/153.4/157

Timelineinfo

09/26/2026 CVE reserved
09/29/2026 +3 days Advisory disclosed
09/29/2026 +0 days VulDB entry created
09/29/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-100818 (🔒)
GCVE (CVE): GCVE-0-2026-100818
GCVE (VulDB): GCVE-100-411390

Entryinfo

Created: 09/29/2026 15:42
Changes: 09/29/2026 15:42 (66)
Complete: 🔍
Cache ID: 216::103

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