CVE-2026-2798 Mozilla CVE debrief

Who should care

Organizations and individuals using Firefox and Thunderbird should prioritize patching this vulnerability to prevent potential exploitation. The vulnerability's high severity and potential for exploitation make it essential for defenders to take immediate action. Additionally, security teams should review their inventory of affected systems and ensure that they are updated to the latest versions.

Technical summary

CVE-2026-2798 is a use-after-free vulnerability in the DOM: Core & HTML component of Firefox and Thunderbird. The vulnerability occurs when the browser's memory management system fails to properly handle objects, leading to a use-after-free condition. This can be exploited by attackers to execute arbitrary code on affected systems. The vulnerability is patched in Firefox 148 and Thunderbird 148. The CVSS vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Defensive priority

High priority should be given to patching this vulnerability in Firefox and Thunderbird. Defenders should review their inventory of affected systems and ensure that they are updated to the latest versions.

Recommended defensive actions

• Patch Firefox and Thunderbird to version 148 or later
• Review inventory of affected systems and ensure they are updated
• Monitor for potential exploitation attempts
• Implement compensating controls to detect and prevent exploitation
• Track exception and remediation efforts

Evidence notes

The CVE record and NVD detail provide further information on this vulnerability. The vulnerability was published on February 24, 2026, and last modified on June 30, 2026. The CVSS score is 8.8, and the severity is classified as HIGH. The CWE for this vulnerability is CWE-416.

Official resources