Mozilla Firefox up to 148 WebRender 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.
6.7$5k-$25k0.00

Summaryinfo

A vulnerability, which was classified as critical, was found in Mozilla Firefox up to 148. The affected element is an unknown function of the component WebRender. Executing a manipulation can lead to use after free. This vulnerability is tracked as CVE-2026-4684. The attack can be launched remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in Mozilla Firefox up to 148 and classified as critical. This vulnerability affects some unknown functionality of the component WebRender. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Race condition, use-after-free in the Graphics: WebRender component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.

The advisory is shared for download at bugzilla.mozilla.org. This vulnerability was named CVE-2026-4684 since 03/24/2026. 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 03/28/2026).

The vulnerability scanner Nessus provides a plugin with the ID 303474 (Mozilla Firefox < 149.0), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 149 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (303474). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.9
VulDB Meta Temp Score: 6.7

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

ADP CISA Base Score: 7.5
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

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 303474
Nessus Name: Mozilla Firefox < 149.0

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Firefox 149

Timelineinfo

03/24/2026 Advisory disclosed
03/24/2026 +0 days CVE reserved
03/24/2026 +0 days VulDB entry created
03/28/2026 +4 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-4684 (🔒)
GCVE (CVE): GCVE-0-2026-4684
GCVE (VulDB): GCVE-100-352732

Entryinfo

Created: 03/24/2026 14:14
Updated: 03/28/2026 17:15
Changes: 03/24/2026 14:14 (56), 03/24/2026 23:11 (2), 03/28/2026 17:15 (13)
Complete: 🔍
Cache ID: 216:045:103

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