CVE-2026-2777

Name: CVE-2026-2777
Creator: NVD / NIST
Published: 2026-02-24T14:16:26.123+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 0.37%

Last modified Jun 17, 2026

CVE-2026-2777 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Privilege escalation in the Messaging System component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.. EPSS estimates a 0.37% chance of exploitation in the next 30 days.

Description

Privilege escalation in the Messaging System component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.37%

28.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-269

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 115.33.0
Mozilla	Firefox	< 148.0
Mozilla	Firefox	>= 128.0, < 140.8.0
Mozilla	Thunderbird	< 140.8.0
Mozilla	Thunderbird	< 148.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2015305Issue Tracking, Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-13/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-14/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-15/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-16/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-17/Vendor Advisory

Timeline

Published: Feb 24, 2026
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2026-2777?

Privilege escalation in the Messaging System component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

How severe is CVE-2026-2777?

CVE-2026-2777 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.37% probability of exploitation in the next 30 days.

How do I fix CVE-2026-2777?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-2777?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST