CVE-2025-4919 Out-of-bounds access when optimizing linear sums

What is CVE-2025-4919?

CVE-2025-4919 is a high-severity memory corruption vulnerability in Mozilla Firefox, published on 17 May 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-787, CWE-125

Which versions are affected by CVE-2025-4919?

It affects 2 products.

Products include Mozilla Firefox, Mozilla Thunderbird.

How do I fix CVE-2025-4919?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2025-4919 being exploited?

There is no known exploitation of CVE-2025-4919 in the wild and no public exploit code.

Other vulnerabilities in Mozilla Firefox

• CVE-2019-11708 Mozilla Firefox and Thunderbird Sandbox Escape Exploited Critical 10.0
• CVE-2010-3765 Mozilla Multiple Products Remote Code Execution Exploited Critical 9.8
• CVE-2022-26486 Mozilla Firefox Use-After-Free Exploited Critical 9.6
• CVE-2022-26485 Mozilla Firefox Use-After-Free Exploited High 8.8
• CVE-2019-11707 Mozilla Firefox and Thunderbird Type Confusion Exploited High 8.8

All Mozilla Firefox vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2025-4919, GHSA-f333-vhwv-jvmx, UBUNTU-CVE-2025-4919.