CVE-2025-1936 Adding %00 and a fake extension to a jar: URL changed the interpretation of the contents

What is CVE-2025-1936?

CVE-2025-1936 is a high-severity vulnerability in Mozilla Firefox, published on 4 Mar 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

jar: URLs retrieve local file content packaged in a ZIP archive. The null and everything after it was ignored when retrieving the content from the archive, but the fake extension after the null was used to determine the type of content. This could have been used to hide code in a web extension disguised as something else like an image. This vulnerability was fixed in Firefox 136, Firefox ESR 128.8, Thunderbird 136, and Thunderbird 128.8.

Weakness: CWE-158

Which versions are affected by CVE-2025-1936?

It affects 2 products.

Products include Mozilla Firefox, Mozilla Thunderbird.

How do I fix CVE-2025-1936?

Upgrade to a fixed version.

Is CVE-2025-1936 being exploited?

There is no known exploitation of CVE-2025-1936 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-2025-1936, GHSA-x4j2-c46q-7jp5, UBUNTU-CVE-2025-1936.