VDB-364672 · CVE-2026-8959 · Nessus 316449

Mozilla Firefox up to 140.10/150 Win32 sandbox

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.
7.8	$5k-$25k	0.00

Summaryinfo

A vulnerability classified as critical was found in Mozilla Firefox up to 140.10/150. Affected by this vulnerability is an unknown functionality of the component Win32. Executing a manipulation can lead to sandbox. This vulnerability is tracked as CVE-2026-8959. The attack can be launched remotely. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as critical was found in Mozilla Firefox up to 140.10/150. This vulnerability affects an unknown function of the component Win32. The manipulation with an unknown input leads to a sandbox vulnerability. The CWE definition for the vulnerability is CWE-265. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

The advisory is shared for download at bugzilla.mozilla.org. This vulnerability was named CVE-2026-8959 since 05/19/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 06/17/2026). The MITRE ATT&CK project declares the attack technique as T1611.

The vulnerability scanner Nessus provides a plugin with the ID 316449 (Linux Distros Unpatched Vulnerability : CVE-2026-8959), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 140.11 or 151 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (316449) and CERT Bund (WID-SEC-2026-1606). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

Debian Linux
Amazon Linux 2
Red Hat Enterprise Linux
SUSE Linux
Oracle Linux
IGEL OS
SUSE openSUSE
RESF Rocky Linux
Mozilla Firefox
Mozilla Firefox ESR
Mozilla Thunderbird

Productinfo

Type

Web Browser

Vendor

Mozilla

Name

Firefox

Version

License

open-source

Website

Vendor: https://www.mozilla.org/
Product: https://www.mozilla.org/en-US/firefox/

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

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

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

Exploitinginfo

Class: Sandbox
CWE: CWE-265 / CWE-264
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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

Nessus ID: 316449
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-8959

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Firefox 140.11/151

Timelineinfo

05/19/2026 Advisory disclosed
05/19/2026 +0 days CVE reserved
05/19/2026 +0 days VulDB entry created
06/17/2026 +29 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-8959 (🔒)
GCVE (CVE): GCVE-0-2026-8959
GCVE (VulDB): GCVE-100-364672
CERT Bund: WID-SEC-2026-1606 - Mozilla Firefox und Thunderbird: Mehrere Schwachstellen

Entryinfo

Created: 05/19/2026 15:56
Updated: 06/17/2026 19:43
Changes: 05/19/2026 15:56 (56), 05/23/2026 12:24 (12), 05/23/2026 18:20 (2), 06/17/2026 19:43 (7)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.