CVE-2026-2774 Mozilla CVE debrief

Who should care

Organizations and individuals using Firefox, Firefox ESR, Thunderbird, or other affected products should prioritize patching this vulnerability. The vulnerability's critical severity and potential for exploitation make it essential for defenders to take immediate action. Red Hat and other vendors have also provided errata and patches for their affected products.

Technical summary

The CVE-2026-2774 vulnerability is caused by an integer overflow in the Audio/Video component of Firefox. This vulnerability can be exploited remotely, and its critical CVSS score indicates a high likelihood of exploitation. The vulnerability affects multiple versions of Firefox, including Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8. The Common Vulnerability and Exposure (CVE) scoring system rates this vulnerability as CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Defensive priority

Defenders should prioritize patching CVE-2026-2774 due to its critical severity and potential for exploitation. Immediate action is necessary to prevent potential attacks.

Recommended defensive actions

• Apply patches for Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
• Review and apply Red Hat errata and patches for affected products.
• Verify that all affected products are updated to the latest versions.
• Monitor for potential exploitation attempts and anomalies.
• Consider implementing compensating controls, such as network segmentation or access restrictions, for high-risk environments.

Evidence notes

The CVE-2026-2774 vulnerability was publicly disclosed on February 24, 2026, and the information was last modified on June 30, 2026. Multiple sources, including Mozilla and Red Hat, have provided advisories and patches for this vulnerability. The Common Vulnerability Scoring System (CVSS) score for this vulnerability is 9.8, indicating a critical severity.

Official resources