CVE-2025-0239
4.0
MEDIUM
CVSS 3.1
EPSS 0.03%
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.
How to fix CVE-2025-0239
To remediate CVE-2025-0239, upgrade the affected package to a fixed version below.
- Debian/firefox-esr—upgrade to 128.6.0esr-1~deb11u3 or later
- —upgrade to 1:128.6.0esr-1~deb11u1 or later
Is CVE-2025-0239 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0, < 128.6.0esr-1~deb11u3
- from 0, < 1:128.6.0esr-1~deb11u1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM4.0 | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |