CSS Parsing Component Site Isolation Flaw Fixed in Firefox 154 & ESR 153.1
CVE-2026-74986 Published on August 18, 2026
Site isolation issue in the CSS Parsing and Computation component
Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Vulnerability Analysis
CVE-2026-74986 is exploitable 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 have a high impact on confidentiality, with no impact on integrity, and a high impact on availability.
Weakness Type
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-2026-74986 has been classified to as an Information Disclosure vulnerability or weakness.
Products Associated with CVE-2026-74986
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Affected Versions
Mozilla Firefox:- Version 153.1, <= 153.* is unaffected.
- Version 154, <= * is unaffected.
- Version 153.1, <= 153.* is unaffected.
- Version 154, <= * is unaffected.