CVE-2025-0239
When using Alt-Svc, ALPN did not properly validate certificates when the original server is redirecting to an insecure site.
Does this matter?
Lower severity and a low EPSS score (0.23%). Track it; it rarely justifies an emergency change on its own.
Description
When using Alt-Svc, ALPN did not properly validate certificates when the original server is redirecting to an insecure site. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.
- CVSS 3.1
- 4.0 MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- EPSS
- 0.23% probability · 13th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-295
- Affected
- mozilla/firefox · mozilla/thunderbird
- Source
- security@mozilla.org
EPSS 0.2% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1929156Issue Tracking, Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2025-01/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-02/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-04/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-05/Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2025/01/msg00004.html
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.