CVE-2025-4918

moderate-risk
Published 2025-05-17

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.

Do I need to act?

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0.99% chance of exploitation
EPSS score — low exploit probability
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
?
Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
9
CVSS 9.8/10 Critical
NETWORK / LOW complexity

Affected Products (4)

Affected Vendors

Mozilla

References (10)

Permissions Required https://bugzilla.mozilla.org/show_bug.cgi?id=1966612
Vendor Advisory 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/
https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html
https://lists.debian.org/debian-lts-announce/2025/05/msg00046.html
Exploit https://www.vicarius.io/vsociety/posts/cve-2025-4918-detect-firefox-out-of-bound...
Exploit https://www.vicarius.io/vsociety/posts/cve-2025-4918-mitigate-firefox-out-of-bou...
45
/ 100
moderate-risk
Severity 32/34 · Critical
Exploitability 3/34 · Minimal
Exposure 10/34 · Low