CVE-2026-8958

Name: CVE-2026-8958
Creator: NVD / NIST
Published: 2026-05-19T14:16:52.17+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.6/10EPSS 0.34%

Last modified Jun 17, 2026

CVE-2026-8958 is a high-severity vulnerability rated 8.6/10 on the CVSS scale. Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.. EPSS estimates a 0.34% chance of exploitation in the next 30 days.

Description

Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Metrics

CVSS 3.1

8.6/10

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

EPSS Probability

0.34%

26.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 140.11.0
Mozilla	Firefox	< 151.0.0
Mozilla	Thunderbird	< 140.11
Mozilla	Thunderbird	< 151.0.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2034713Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-46/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-48/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-50/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-51/Vendor Advisory

Timeline

Published: May 19, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-8958?

Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

How severe is CVE-2026-8958?

CVE-2026-8958 has a CVSS score of 8.6/10 (HIGH severity). The EPSS model estimates a 0.34% probability of exploitation in the next 30 days.

How do I fix CVE-2026-8958?

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-2026-8958?

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

Scan your code now

Source: NVD / NIST