CVE-2026-2776

Name: CVE-2026-2776
Creator: NVD / NIST
Published: 2026-02-24T14:16:26.023+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 10/10EPSS 0.49%

Last modified Jun 17, 2026

CVE-2026-2776 is a critical-severity vulnerability rated 10/10 on the CVSS scale. Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.. EPSS estimates a 0.49% chance of exploitation in the next 30 days.

Description

Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. 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

10/10

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

EPSS Probability

0.49%

38.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-119

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=2015266Issue 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-2026-2776?

How severe is CVE-2026-2776?

CVE-2026-2776 has a CVSS score of 10/10 (CRITICAL severity). The EPSS model estimates a 0.49% probability of exploitation in the next 30 days.

How do I fix CVE-2026-2776?

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-2026-2776?

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

Scan your code now

Source: NVD / NIST