Mozilla Firefox up to 135 jar URL null byte or nul character

Summaryinfo

A vulnerability identified as problematic has been detected in Mozilla Firefox up to 135. This affects an unknown part of the component jar URL Handler. This manipulation causes an unknown weakness. This vulnerability is handled as CVE-2025-1936. The attack can be initiated remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Mozilla Firefox up to 135. Affected by this vulnerability is some unknown functionality of the component jar URL Handler. The CWE definition for the vulnerability is CWE-158. The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes NUL characters or null bytes when they are sent to a downstream component. As an impact it is known to affect integrity. The summary by CVE is:

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.

It is possible to read the advisory at bugzilla.mozilla.org. This vulnerability is known as CVE-2025-1936 since 03/04/2025. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 04/15/2026).

The vulnerability scanner Nessus provides a plugin with the ID 232152 (Linux Distros Unpatched Vulnerability : CVE-2025-1936), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 136 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (232152). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Web Browser

Vendor

• Mozilla

Name

• Firefox

Version

• 135

License

• open-source

Website

• Vendor: https://www.mozilla.org/
• Product: https://www.mozilla.org/en-US/firefox/

CPE 2.3info

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CPE 2.2info

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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