CVE-2025-4919

Firefox vulnerability

CVSS

8.8

EPSS

6.2%

EPSS pct

93th

Exploited

No known

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.

Affected vendor

Mozilla

Affected product

Firefox

CVSS vector

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

Weakness type (CWE)

CWE-125 — Out-of-bounds Read
CWE-787 — Out-of-bounds Write

Published

2025-05-17

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, user interaction. Successful exploitation leads to high impact to confidentiality, high impact to integrity, high impact to availability.

Its EPSS score of 6.2% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 93% of all scored CVEs.

Check your external exposure to CVE-2025-4919

Confirm whether Mozilla Firefox is running on any internet-facing host or subdomain.
Match discovered service fingerprints against the version affected by CVE-2025-4919.
Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2025-4919

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