Vulnerability in Mozilla Firefox
CVE-2025-5271
Previewing a response in Devtools ignored CSP headers, which could have allowed content injection attacks. This vulnerability was fixed in Firefox 139 and Thunderbird 139.
EPSS: 0.003 (18.7th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
Affected products
- Mozilla Firefox — versions 139
- Mozilla Thunderbird — versions 139
Weakness classification (CWE)
References
- security@mozilla.org (Permissions Required)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org
Frequently asked questions
- What is CVE-2025-5271?
- CVE-2025-5271 is a medium-severity vulnerability in Mozilla Firefox, classified under Improper Encoding or Escaping of Output. CVSS score: 6.5/10. Published 2025-05-27.
- How severe is CVE-2025-5271?
- Medium severity. CVSS v3 base score is 6.5 out of 10.