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 was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

PUBLISHED Reserved 2025-06-20 | Published 2025-06-24 | Updated 2026-04-13 | Assigner mozilla

Product status

Credits

Masato Kinugawa

References

lists.debian.org/debian-lts-announce/2025/07/msg00002.html

lists.debian.org/debian-lts-announce/2025/06/msg00029.html

bugzilla.mozilla.org/show_bug.cgi?id=1970658

www.mozilla.org/security/advisories/mfsa2025-51/

www.mozilla.org/security/advisories/mfsa2025-53/

www.mozilla.org/security/advisories/mfsa2025-54/

www.mozilla.org/security/advisories/mfsa2025-55/

cve.org (CVE-2025-6429)

nvd.nist.gov (CVE-2025-6429)

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