CVE-2020-26966

Name: CVE-2020-26966
Creator: NVD / NIST
Published: 2020-12-09T01:15:13.58+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.34%

Last modified Jun 17, 2026

CVE-2020-26966 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. Searching for a single word from the address bar caused an mDNS request to be sent on the local network searching for a hostname consisting of that string; resulting in an information leak. *Note: This issue only affected Windows operating systems. EPSS estimates a 1.34% chance of exploitation in the next 30 days.

Description

Searching for a single word from the address bar caused an mDNS request to be sent on the local network searching for a hostname consisting of that string; resulting in an information leak. *Note: This issue only affected Windows operating systems. Other operating systems are unaffected.*. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

EPSS Probability

1.34%

67.7th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 83.0
Mozilla	Firefox Esr	< 78.5
Mozilla	Thunderbird	< 78.5

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1663571Issue Tracking, Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-50/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-51/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-52/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1663571Issue Tracking, Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-50/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-51/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-52/Vendor Advisory

Timeline

Published: Dec 9, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-26966?

How severe is CVE-2020-26966?

CVE-2020-26966 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.34% probability of exploitation in the next 30 days.

How do I fix CVE-2020-26966?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-26966?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST