Vulnerability in Mozilla Firefox
CVE-2025-5270
In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled. This vulnerability was fixed in Firefox 139 and Thunderbird 139.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.003 (19.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 19th percentile — 19.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Mozilla Firefox — versions 139
- Mozilla Thunderbird — versions 139
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2025-42/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-45/
Frequently asked questions
- What is CVE-2025-5270?
- CVE-2025-5270 is a high-severity vulnerability in Mozilla Firefox, classified under Cleartext Transmission of Sensitive Information. CVSS score: 7.5/10. Published 2025-05-27.
- How severe is CVE-2025-5270?
- High severity. CVSS v3 base score is 7.5 out of 10.