ZeroDay Findings
Sign inSign up

Vulnerabilities

Vulnerability · CVE-2025-5270

In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled.

Published May 27, 2025 · catalog updated Apr 13, 2026 · mozilla

Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.3%
Remediation
Advisory link
Affected products
vendor mozilla

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.

Technical analysis

Mechanism and impact are interpreted from ingested advisories — not independent exploit research.

  • CWE classification

    No CWE identifiers stored yet.

  • Prerequisites and impact

    Follow the original vendor advisory for access prerequisites and impact. This catalog does not invent exploit conditions.

How to fix CVE-2025-5270

What to do

Three reads of the same public record: the decision, the versions on file, and the signals. Confirm the vendor advisory before you patch. This page does not publish exploit steps.

Executive

This is a public record, not a confirmed incident. CVE-2025-5270 is a high issue in mozilla (CVSS 7.5). CISA does not currently list it as known exploited. Next step: Compare installed versions with the linked vendor advisory before changing production.

System administrator

Check whether mozilla is installed. Ranges on record: mozilla. Compare installed versions with the linked vendor advisory before changing production.

Security analyst

CVSS 7.5. EPSS 0.3%. CISA does not currently list it as known exploited. Weaknesses: not classified. Sources: epss, euvd. Exploit links, when listed below, point at the original publisher.

Related intelligence

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 27, 2025 · EUVD

    Detected

    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.

  2. Apr 13, 2026 · EUVD

    Updated

    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 versions

Enter an installed version to get a verified affected / not-affected result against the ranges below.

  • vendor mozillaversion unspecified

Sources

  • FIRST EPSSExploitation probabilityCVE-2025-5270

    30-day exploitation probability 0.3%

    first.org
  • EUVDVulnerability recordEUVD-2025-18106

    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.

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.