Mitigation Bypass in Firefox's HTML Parser Component by Mozilla
CVE-2026-2775

9.8CRITICAL

Key Information:

Vendor

Mozilla
Status
Firefox
Firefox Esr
Thunderbird
Vendor
CVE Published:
24 February 2026

What is CVE-2026-2775?

A mitigation bypass vulnerability exists within the HTML Parser component of Firefox, which can result in unintended behavior and security risks. This issue affects multiple versions of Firefox, specifically those prior to version 148, as well as Firefox ESR versions less than 115.33 and 140.8. Users are advised to upgrade to the latest versions to ensure enhanced security and protection from potential exploits.

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Deploy the Patch

Affected Version(s)

Firefox < 148

Firefox ESR < 115.33

Firefox ESR < 140.8

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2015199
https://www.mozilla.org/security/advisories/mfsa2026-13/
https://www.mozilla.org/security/advisories/mfsa2026-14/

CVSS V3.1

Score:
9.8
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

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