Site Isolation Issue in Firefox Networking Component (fixed in 153/140.13)
CVE-2026-16387 Published on July 21, 2026
Site isolation issue in the Networking component
Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
Vulnerability Analysis
CVE-2026-16387 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Weakness Types
Origin Validation Error
The software does not properly verify that the source of data or communication is valid.
What is an Authorization Vulnerability?
The software does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
CVE-2026-16387 has been classified to as an Authorization vulnerability or weakness.
What is an Information Disclosure Vulnerability?
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
CVE-2026-16387 has been classified to as an Information Disclosure vulnerability or weakness.
Products Associated with CVE-2026-16387
stack.watch emails you whenever new vulnerabilities are published in Mozilla Firefox or Mozilla Thunderbird. Just hit a watch button to start following.
Affected Versions
Mozilla Firefox:- Version 140.13, <= 140.* is unaffected.
- Version 153, <= * is unaffected.
- Version 140.13, <= 140.* is unaffected.
- Version 153, <= * is unaffected.