CVE-2025-4919: firefox Out-of-bounds Read — Fix

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.

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CVSS v3.1 Score

8.8

HIGH

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

Affected Products

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

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2025-36/ https://www.mozilla.org/security/advisories/mfsa2025-37/ https://www.mozilla.org/security/advisories/mfsa2025-38/ https://www.mozilla.org/security/advisories/mfsa2025-40/ https://www.mozilla.org/security/advisories/mfsa2025-41/

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=1966614 https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html https://lists.debian.org/debian-lts-announce/2025/05/msg00046.html

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. It has a CVSS v3.1 base score of 8.8 (HIGH).

How severe is CVE-2025-4919? +

CVE-2025-4919 has a CVSS v3.1 score of 8.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-4919? +

CVE-2025-4919 affects products from mozilla, specifically: firefox, thunderbird. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-4919? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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