CVE-2026-12291

Name: CVE-2026-12291
Creator: NVD / NIST
Published: 2026-06-16T13:16:29.363+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 0.30%

Last modified Jun 18, 2026

CVE-2026-12291 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.. EPSS estimates a 0.30% chance of exploitation in the next 30 days.

Description

Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

Metrics

CVSS 3.1

8.8/10

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

EPSS Probability

0.30%

22.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-416

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 115.37.0
Mozilla	Firefox	< 152.0.0
Mozilla	Firefox	>= 128.0, < 140.12.0
Mozilla	Thunderbird	< 140.12.0
Mozilla	Thunderbird	< 152.0.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2036929Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-57/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-58/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-59/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-60/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-61/Vendor Advisory

Timeline

Published: Jun 16, 2026
Last Modified: Jun 18, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-12291?

Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

How severe is CVE-2026-12291?

CVE-2026-12291 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.30% probability of exploitation in the next 30 days.

How do I fix CVE-2026-12291?

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-2026-12291?

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

Scan your code now

Source: NVD / NIST