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Fencer Vulns
medium 6.5

CVE-2021-23982 json

Using techniques that built on the slipstream research, a malicious webpage could have scanned both an internal network's hosts as well as…

published 2021-03-31 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-10902

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

Summary

Using techniques that built on the slipstream research, a malicious webpage could have scanned both an internal network's hosts as well as services running on the user's local machine utilizing WebRTC connections. This vulnerability affects Firefox ESR < 78.9, Firefox < 87, and Thunderbird < 78.9.

Patch / fix

  • Mozilla Firefox ESR 78.9
  • Mozilla Firefox 87
  • Mozilla Thunderbird 78.9
  • firefox-esr Debian 14, Debian 13, Debian 12 78.9.0esr-1
  • thunderbird Debian 14, Debian 13, Debian 12 1:78.9.0-1

debian advisories DEBIAN-CVE-2021-23982

  • firefox Ubuntu 16.04 LTS 87.0+build3-0ubuntu0.16.04.2
  • firefox Ubuntu 18.04 LTS 87.0+build3-0ubuntu0.18.04.2
  • firefox Ubuntu 20.04 LTS 87.0+build3-0ubuntu0.20.04.2
  • thunderbird Ubuntu 18.04 LTS 1:78.11.0+build1-0ubuntu0.18.04.2
  • thunderbird Ubuntu 20.04 LTS 1:78.11.0+build1-0ubuntu0.20.04.2

ubuntu advisories UBUNTU-CVE-2021-23982

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • thunderbird RHEL 7 78.9.0-3.el7_9
  • firefox RHEL 7 78.9.0-1.el7_9
  • thunderbird RHEL 8 78.9.0-3.el8_3
  • firefox RHEL 8 78.9.0-1.el8_3
  • firefox RHEL 8.1 EUS 78.9.0-1.el8_1
  • thunderbird RHEL 8.2 EUS 78.9.0-3.el8_2
  • thunderbird RHEL 8.1 EUS 78.9.0-3.el8_1
  • firefox RHEL 8.2 EUS 78.9.0-1.el8_2

red hat advisories RHSA-2021:0996RHSA-2021:0991RHSA-2021:0994RHSA-2021:0992RHSA-2021:0995RHSA-2021:0993

  • MozillaThunderbird SLE Workstation Extension 15 SP2 78.9.1-8.20.1
  • MozillaFirefox SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +10 more 78.9.0-3.136.1
  • mozilla-nspr SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +12 more 4.25.1-3.17.1
  • MozillaFirefox-branding-SLE SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +10 more 78-4.16.1
  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +14 more 78.9.0-112.54.1
  • MozillaFirefox SLE Module for Desktop Applications 15 SP2 78.9.0-8.35.1
  • MozillaFirefox SLES 11 SP4-LTSS 78.9.0-78.123.1

suse advisories SUSE-SU-2021:1167-1SUSE-SU-2021:1007-1SUSE-SU-2021:14684-1SUSE-SU-2021:0999-1SUSE-SU-2021:0966-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2
  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • MozillaThunderbird openSUSE Leap 15.2 78.9.1-lp152.2.38.1
  • MozillaFirefox openSUSE Leap 15.2 78.9.0-lp152.2.52.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1openSUSE-SU-2024:10601-1openSUSE-SU-2021:0580-1openSUSE-SU-2021:0487-1

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +8 more 87.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 87.0-r0
  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 78.9.0-r0
  • thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 78.9.0-r0

alpine advisories ALPINE-CVE-2021-23982

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

  • firefox Arch Linux 87.0-1
  • thunderbird Arch Linux 78.9.0-1

arch linux advisories AVG-1728AVG-1729

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-2021-23982 updated cvss 6.1

Mozilla: Internal network hosts could have been probed by a malicious webpage

  • Red Hat Enterprise Linux 6 firefox, thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) firefox 78.9.0-1.el8_3, thunderbird 78.9.0-3.el8_3
    fixed: vendor fix RHSA-2021:0990
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox 78.9.0-1.el8_1, thunderbird 78.9.0-3.el8_1
    fixed: vendor fix RHSA-2021:0991
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) firefox 78.9.0-1.el8_2, thunderbird 78.9.0-3.el8_2
    fixed: vendor fix RHSA-2021:0989
  • Red Hat Enterprise Linux Client (v. 7) firefox 78.9.0-1.el7_9, thunderbird 78.9.0-3.el7_9 Red Hat Enterprise Linux Client Optional (v. 7) firefox 78.9.0-1.el7_9 Red Hat Enterprise Linux Server (v. 7) firefox 78.9.0-1.el7_9 Red Hat Enterprise Linux Server Optional (v. 7) firefox 78.9.0-1.el7_9, thunderbird 78.9.0-3.el7_9 Red Hat Enterprise Linux Workstation (v. 7) firefox 78.9.0-1.el7_9, thunderbird 78.9.0-3.el7_9 Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 78.9.0-1.el7_9
    fixed: vendor fix RHSA-2021:0992

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

0.74% chance of exploitation in the next 30 days, higher than 54% 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:N/I:H/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N

Affected products

  • Mozilla Firefox ESR
  • Mozilla Firefox
  • Mozilla Thunderbird

Classification

Weakness
  • CWE-326 Inadequate Encryption Strength

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.