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Fencer Vulns
medium 6.5

CVE-2020-26966 json

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…

published 2020-12-09 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-19490

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

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.

Patch / fix

  • mozilla firefox 83.0
  • mozilla firefox_esr 78.5
  • mozilla thunderbird 78.5
  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 78.5.0-112.36.1
  • MozillaThunderbird SLE Workstation Extension 15 SP2, SLE Workstation Extension 15 SP1 78.5.0-3.107.1
  • MozillaFirefox SLE Module for Desktop Applications 15 SP2 78.5.0-8.17.1
  • MozillaFirefox SLE Module for Desktop Applications 15 SP1 78.5.0-3.119.1
  • MozillaFirefox SLES 11 SP4-LTSS 78.5.0-78.105.1

suse advisories SUSE-SU-2020:3548-1SUSE-SU-2020:3528-1SUSE-SU-2020:3458-1SUSE-SU-2020:14548-1SUSE-SU-2020:3383-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2
  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaFirefox openSUSE Leap 15.2 78.5.0-lp152.2.33.1
  • MozillaThunderbird openSUSE Leap 15.1 78.5.0-lp151.2.59.1
  • MozillaThunderbird openSUSE Leap 15.2 78.5.0-lp152.2.19.1
  • MozillaFirefox openSUSE Leap 15.1 78.5.0-lp151.2.79.1
  • MozillaFirefox openSUSE Leap 15.2 78.5.0-lp152.2.30.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1openSUSE-SU-2024:10601-1openSUSE-SU-2020:2315-1openSUSE-SU-2020:2187-1openSUSE-SU-2020:2096-1

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 83.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 83.0-r0
  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 78.5.0-r0
  • thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 78.5.1-r0

alpine advisories ALPINE-CVE-2020-26966

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-26966 updated cvss 6.5

Mozilla: Single-word search queries were also broadcast to local network

  • Red Hat Enterprise Linux 5 firefox Red Hat Enterprise Linux 6 firefox Red Hat Enterprise Linux 7 firefox Red Hat Enterprise Linux 8 firefox
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.35% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:P/I:N/A:N

Affected products

  • Mozilla Firefox
  • Mozilla Firefox ESR
  • Mozilla Thunderbird

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.