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HIGH

CVE-2025-4919

CVSS v3

8.8

HIGH

EPSS Score

8.6 %

exploit probability, as of 2026-09-25

CISA KEV

No

known exploited

Exploitation

—

SSVC status

Description

An attacker was able to perform an out-of-bounds read or write on a JavaScript object by confusing array index sizes. 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.

Technical details

Published
2025-05-17
Last Modified
2026-04-13

Frequently asked questions

What is CVE-2025-4919?

An attacker was able to perform an out-of-bounds read or write on a JavaScript object by confusing array index sizes. 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.

Is CVE-2025-4919 actively exploited?

Active exploitation of CVE-2025-4919 has not been confirmed. Its EPSS score was 8.6% on 2026-09-25, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2025-4919?

CVE-2025-4919 has a CVSS v3 base score of 8.8 (HIGH severity).

Is CVE-2025-4919 affecting your environment?

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