CVE-2025-6429
Incorrect parsing of URLs could have allowed embedding of youtube.com
CVSS Score
6.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| Vendor | mozilla |
| Product | firefox |
| Ecosystems | |
| Industries | Technology |
| Published | Jun 24, 2025 |
| Last Updated | Apr 13, 2026 |
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Affected Versions
Mozilla / Firefox
All versions affected Mozilla / Thunderbird
All versions affected References
bugzilla.mozilla.org: https://bugzilla.mozilla.org/show_bug.cgi?id=1970658 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-51/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-53/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-54/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-55/ lists.debian.org: https://lists.debian.org/debian-lts-announce/2025/07/msg00002.html lists.debian.org: https://lists.debian.org/debian-lts-announce/2025/06/msg00029.html
Credits
Masato Kinugawa