CVE-2025-4918

Name: CVE-2025-4918
Creator: NVD / NIST
Published: 2025-05-17T22:15:19.563+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 8.62%

Last modified Jun 17, 2026

CVE-2025-4918 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. An attacker was able to perform an out-of-bounds read or write on a JavaScript `Promise` object. This vulnerability was fixed in Firefox 138.0.4, Firefox ESR 128.10.1, Firefox ESR 115.23.1, Thunderbird 128.10.2, and Thunderbird 138.0.2.. EPSS estimates a 8.62% chance of exploitation in the next 30 days.

Description

An attacker was able to perform an out-of-bounds read or write on a JavaScript `Promise` object. This vulnerability was fixed in Firefox 138.0.4, Firefox ESR 128.10.1, Firefox ESR 115.23.1, Thunderbird 128.10.2, and Thunderbird 138.0.2.

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

8.62%

94.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 115.23.1
Mozilla	Firefox	< 138.0.4
Mozilla	Firefox	>= 116.0, < 128.10.1
Mozilla	Thunderbird	< 128.10.2
Mozilla	Thunderbird	>= 138.0, < 138.0.2

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1966612Permissions Required
https://www.mozilla.org/security/advisories/mfsa2025-36/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-37/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-38/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-40/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-41/Vendor Advisory
https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html
https://lists.debian.org/debian-lts-announce/2025/05/msg00046.html
https://www.vicarius.io/vsociety/posts/cve-2025-4918-detect-firefox-out-of-bounds-writeExploit, Third Party Advisory
https://www.vicarius.io/vsociety/posts/cve-2025-4918-mitigate-firefox-out-of-bounds-writeExploit, Third Party Advisory

Timeline

Published: May 17, 2025
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2025-4918?

How severe is CVE-2025-4918?

CVE-2025-4918 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 8.62% probability of exploitation in the next 30 days.

How do I fix CVE-2025-4918?

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-2025-4918?

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

Scan your code now

Source: NVD / NIST