Mozilla Firefox up to 140.12/152 Networking isolation

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.
6.0$5k-$25k0.00

Summaryinfo

A vulnerability was found in Mozilla Firefox up to 140.12/152 and classified as critical. This affects an unknown part of the component Networking. Such manipulation leads to isolation. This vulnerability is listed as CVE-2026-16387. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in Mozilla Firefox up to 140.12/152. It has been rated as critical. Affected by this issue is an unknown code of the component Networking. The manipulation with an unknown input leads to a isolation vulnerability. Using CWE to declare the problem leads to CWE-653. The product does not properly compartmentalize or isolate functionality, processes, or resources that require different privilege levels, rights, or permissions. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13.

The advisory is shared for download at bugzilla.mozilla.org. This vulnerability is handled as CVE-2026-16387 since 07/20/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for 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 08/08/2026).

The vulnerability scanner Nessus provides a plugin with the ID 333348 (AlmaLinux 8 : firefox (ALSA-2026:47105)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 140.13 or 153 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (333348). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

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Version

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Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.3
VulDB Meta Temp Score: 6.0

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
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: Isolation
CWE: CWE-653
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: 333348
Nessus Name: AlmaLinux 8 : firefox (ALSA-2026:47105)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
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
08/08/2026 +18 days VulDB entry last update

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: bugzilla.mozilla.org
Status: Confirmed

CVE: CVE-2026-16387 (🔒)
GCVE (CVE): GCVE-0-2026-16387
GCVE (VulDB): GCVE-100-380888

Entryinfo

Created: 07/21/2026 15:54
Updated: 08/08/2026 08:17
Changes: 07/21/2026 15:54 (54), 08/08/2026 08:17 (5)
Complete: 🔍
Cache ID: 216::103

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

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