CVE-2025-6429

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 affects Firefox < 140 and Firefox ESR < 128.12.

Category

6.5
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 0.02%
Vendor Advisory mozilla.org Vendor Advisory mozilla.org
Affected: Mozilla Firefox
Affected: Mozilla Firefox ESR
Published at:
Updated at:

References

Link Tags
https://bugzilla.mozilla.org/show_bug.cgi?id=1970658 permissions required
https://www.mozilla.org/security/advisories/mfsa2025-51/ vendor advisory
https://www.mozilla.org/security/advisories/mfsa2025-53/ vendor advisory

Frequently Asked Questions

What is the severity of CVE-2025-6429?
CVE-2025-6429 has been scored as a medium severity vulnerability.
How to fix CVE-2025-6429?
To fix CVE-2025-6429, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2025-6429 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2025-6429 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2025-6429?
CVE-2025-6429 affects Mozilla Firefox, Mozilla Firefox ESR.
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