CVE-2025-6429: Mozilla Firefox · CWE-116
Affects Mozilla FirefoxSource CVE Database V5
Not known to be exploited · CVSS 6.5 Medium : upgrade to 140 when convenient.
Data as of 26 Oct 2026, 08:30 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 28% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 140
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
Weaponised: 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 26 Oct 2026.
What to do
Upgrade Mozilla Firefox to 140.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Mozilla Firefox | Affected
| Fixed in
|
AI-suggested
This vulnerability has been fixed in Firefox 140 and Firefox ESR 128.12. Users and administrators should update to these versions or later to remediate this issue. Since this is a client-side browser vulnerability, applying the official Mozilla updates fully mitigates the risk.
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.
References
- bugzilla.mozilla.org/show_bug.cgi?id=1970658 (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)
- lists.debian.org/debian-lts-announce/2025/07/msg00002.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/06/msg00029.html (opens in a new tab)