Mozilla Firefox up to 140.12/152 WebExtensions Remote Code Execution

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.
7.0$5k-$25k1.11

Summaryinfo

A vulnerability classified as critical has been found in Mozilla Firefox up to 140.12/152. Affected by this vulnerability is an unknown functionality of the component WebExtensions. The manipulation leads to Remote Code Execution. This vulnerability is uniquely identified as CVE-2026-16396. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in Mozilla Firefox up to 140.12/152. It has been rated as critical. This issue affects some unknown processing of the component WebExtensions. The manipulation with an unknown input leads to a remote code execution vulnerability. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Privilege escalation in WebExtensions. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13.

The advisory is shared at bugzilla.mozilla.org. The identification of this vulnerability is CVE-2026-16396 since 07/20/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 07/21/2026).

Upgrading to version 140.13 or 153 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best 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: 7.3
VulDB Meta Temp Score: 7.0

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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

Exploitinginfo

Class: Remote Code Execution
CWE: Unknown
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: no mitigation known
Status: 🔍

0-Day Time: 🔒

Upgrade: Firefox 140.13/153

Timelineinfo

07/20/2026 CVE reserved
07/21/2026 +1 days Advisory disclosed
07/21/2026 +0 days VulDB entry created
07/21/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-16396 (🔒)
GCVE (CVE): GCVE-0-2026-16396
GCVE (VulDB): GCVE-100-380897

Entryinfo

Created: 07/21/2026 16:03
Changes: 07/21/2026 16:03 (53)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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