What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-03-04 · updated 2026-10-05
• Weakness: CWE-158

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.

Affected products

• Mozilla Firefox: before 128.8.0; before 136.0 — fixed in 128.8.0, 136.0
• Mozilla Thunderbird: before 128.8.0; from 129.0 before 136.0 — fixed in 128.8.0, 136.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 128.8.0, 136.0; Mozilla Thunderbird 128.8.0, 136.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1940027
• https://www.mozilla.org/security/advisories/mfsa2025-14/
• https://www.mozilla.org/security/advisories/mfsa2025-16/
• https://www.mozilla.org/security/advisories/mfsa2025-17/
• https://www.mozilla.org/security/advisories/mfsa2025-18/
• https://lists.debian.org/debian-lts-announce/2025/03/msg00006.html

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