CVE-2025-6429 Incorrect parsing of URLs could have allowed embedding of youtube.com
Incorrect URL parsing in Firefox allowed bypassing domain restrictions for embedded content, enabling unauthorized embedding of youtube.com.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2025-6429?
CVE-2025-6429 is a medium-severity 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
Firefox could have incorrectly parsed a URL and rewritten it to the youtube.com domain when parsing the URL specified in an `embed` tag. This could have bypassed website security checks that restricted which domains users were allowed to embed. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.
Weakness: CWE-116
Which versions are affected by CVE-2025-6429?
It affects 1 product.
Products include Mozilla Firefox.
How do I fix CVE-2025-6429?
Upgrade to a fixed version.
Is CVE-2025-6429 being exploited?
There is no known exploitation of CVE-2025-6429 in the wild and no public exploit code.
Other vulnerabilities in Mozilla Firefox
Sources
Also known as DEBIAN-CVE-2025-6429, GHSA-8r38-4g4q-hgvw, UBUNTU-CVE-2025-6429.