CVE-2025-6429Incorrect parsing of URLs could have allowed embedding of youtube.com
- 6.5MediumCVSS base score
- 0.35%Exploitation in 30 daysEPSS · top 71% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By mozilla
- 4 days later
· 4 days later
Published
- 10 months later
· 10 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N |
| NVDNVD · Modified | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.35% · top 71% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
- unaffected 128.12 – ≤ 128.*
- unaffected 140 – ≤ *
- unaffected 128.12 – ≤ 128.*
- unaffected 140 – ≤ *
References
References7
- https://bugzilla.mozilla.org/show_bug.cgi?id=1970658 (opens in a new tab)
- https://www.mozilla.org/security/advisories/mfsa2025-51/ (opens in a new tab)
- https://www.mozilla.org/security/advisories/mfsa2025-53/ (opens in a new tab)
- https://www.mozilla.org/security/advisories/mfsa2025-54/ (opens in a new tab)
- https://www.mozilla.org/security/advisories/mfsa2025-55/ (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2025/07/msg00002.html (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2025/06/msg00029.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2025-21378 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2025-6429)Record last updated .