CVE-2025-6430 Content-Disposition header ignored when a file is included in an embed or object tag

What is CVE-2025-6430?

CVE-2025-6430 is a medium-severity cross-site scripting vulnerability in Mozilla Firefox, published on 24 Jun 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

When a file download is specified via the `Content-Disposition` header, that directive would be ignored if the file was included via a `<embed>` or `<object>` tag, potentially making a website vulnerable to a cross-site scripting attack. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

Weakness: CWE-79

Which versions are affected by CVE-2025-6430?

It affects 1 product.

Products include Mozilla Firefox.

How do I fix CVE-2025-6430?

Upgrade to a fixed version.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2025-6430 being exploited?

There is no known exploitation of CVE-2025-6430 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-2025-6430, GHSA-fvqv-c5hj-jcrp, UBUNTU-CVE-2025-6430.