{"id":"CVE-2025-6429","title":"Firefox could have incorrectly parsed a URL and rewritten it to the youtube.com domain when parsing the URL specified in an `embed` tag","summary":"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 t…","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N","cwe":["CWE-116"],"vendor":"mozilla","product":"firefox","affected":["firefox < 128.12.0","firefox < 140.0"],"patched":["firefox 140.0"],"published":"2025-06-24","updated":"2026-09-30","sourceUpdated":"2026-09-30T18:10:00.190","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-6429","references":[{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1970658","label":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2025-51/","label":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2025-53/","label":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2025-54/","label":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2025-55/","label":"security@mozilla.org"},{"url":"https://lists.debian.org/debian-lts-announce/2025/06/msg00029.html","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2025/07/msg00002.html","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd"],"epss":0.00355,"epssPercentile":0.26824,"ingestedAt":"2026-09-30T18:17:24.444Z","slug":"CVE-2025-6429","body":"## Overview\n\nFirefox 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.\n\n## Affected\n\n- `firefox < 128.12.0`\n- `firefox < 140.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `firefox 140.0`","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}