CVE-2025-6429: Firefox could have incorrectly parsed a URL and rewritten it to the youtube.com domain when parsing
Source GCVE Database
Not known to be exploited · CVSS 6.5 Medium.
Data as of 29 Oct 2026, 22:52 UTC
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 24 Jun 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
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.
References
- nvd.nist.gov/vuln/detail/CVE-2025-6429 (opens in a new tab)
- bugzilla.mozilla.org/show_bug.cgi?id=1970658 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/06/msg00029.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/07/msg00002.html (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-51 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-53 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-54 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2025-55 (opens in a new tab)