7.5HIGH

CVE-2025-5270 — In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled.

Mozilla · Firefox · Published 27 May 2025 · Modified 30 Sept 2026

Description

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.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1910298
https://www.mozilla.org/security/advisories/mfsa2025-42/
https://www.mozilla.org/security/advisories/mfsa2025-45/

What to do

Check whether Firefox is in your asset inventory.
Patch in the next maintenance window; prioritise internet-facing systems.
Record the decision in your risk register for audit evidence.

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Link: adminadda.com/cve/CVE-2025-5270