What’s Vulnerable › Vulnerabilities

CVE-2025-5270: SNI was sometimes unencrypted

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-05-27 · updated 2026-09-30
• Weakness: CWE-319

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.

Affected products

• Mozilla Firefox: before 139.0 — fixed in 139.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 139.0. Check the vendor advisory for mitigations.

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/

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