CVE-2025-5271

MEDIUM 6.5CVE-2025-5271 · Published 27/05/2025 · updated 30/09/2026

In short

CVE-2025-5271 is a MEDIUM (CVSS 6.5) vulnerability affecting firefox (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.30%, higher than 23.4% of all vulnerabilities.
Fix: update to 139.0 or later.

Package	Affected versions	Patched versions
firefox mozilla	`< 139.0`	`139.0`

Description

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.

References

bugzilla.mozilla.org/show_bug.cgi · Permissions Required
mozilla.org/security/advisories/mfsa2025-42 · Vendor Advisory
mozilla.org/security/advisories/mfsa2025-45

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Package

Affected versions

Patched versions

firefox

mozilla

< 139.0

139.0

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