critical 9.8

CVE-2020-6814 json

Mozilla developers reported memory safety bugs present in Firefox and Thunderbird 68.5.

published 2020-03-25 6y ago modified 2026-06-17 4mo ago also EUVD-2020-27960

cvss: 9.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.9%; EPSS 1.9% chance of exploitation in 30 days, percentile 79%
public exploits: 0; none known

Mozilla developers reported memory safety bugs present in Firefox and Thunderbird 68.5. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Thunderbird < 68.6, Firefox < 74, Firefox < ESR68.6, and Firefox ESR < 68.6.

Patch / fix

fixed in 3 distros 7

Mozilla Thunderbird 68.6
Mozilla Firefox 74, ESR68.6
Mozilla Firefox ESR 68.6

debian ubuntu red hat suse opensuse alpine arch linux

firefox-esr Debian 14, Debian 13, Debian 12 68.6.0esr-1
thunderbird Debian 14, Debian 13, Debian 12 1:68.6.0-1

debian advisories DEBIAN-CVE-2020-6814

firefox Ubuntu 16.04 LTS 74.0+build3-0ubuntu0.16.04.1
firefox Ubuntu 18.04 LTS 74.0+build3-0ubuntu0.18.04.1
firefox Ubuntu 20.04 LTS 74.0+build3-0ubuntu1
thunderbird Ubuntu 16.04 LTS 1:68.7.0+build1-0ubuntu0.16.04.2
thunderbird Ubuntu 18.04 LTS 1:68.7.0+build1-0ubuntu0.18.04.1
thunderbird Ubuntu 20.04 LTS 1:68.6.0+build2-0ubuntu1

ubuntu advisories UBUNTU-CVE-2020-6814

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 8 68.6.0-1.el8_1
thunderbird RHEL 6 68.6.0-1.el6_10
thunderbird RHEL 7 68.6.0-1.el7_7
firefox RHEL 8 68.6.0-1.el8_1
firefox RHEL 7 68.6.0-1.el7_7
firefox RHEL 6 68.6.0-1.el6_10
thunderbird RHEL 8.0 E4S 68.6.0-1.el8_0
firefox RHEL 8.0 E4S 68.6.0-1.el8_0

red hat advisories RHSA-2020:0919 RHSA-2020:0914 RHSA-2020:0918 RHSA-2020:0905 RHSA-2020:0820 RHSA-2020:0819

MozillaThunderbird SLE Workstation Extension 15 SP1 68.6.0-3.74.1
MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +16 more 68.6.0-109.110.1
MozillaFirefox SLE Module for Desktop Applications 15 SP1 68.6.0-3.75.1
MozillaFirefox SLES 11 SP4-LTSS 68.6.0-78.64.1

suse advisories SUSE-SU-2020:0721-1 SUSE-SU-2020:0717-1 SUSE-SU-2020:0686-1 SUSE-SU-2020:14312-1

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 15.1 68.6.0-lp151.2.28.1
MozillaFirefox openSUSE Leap 15.1 68.6.0-lp151.2.33.1

opensuse advisories openSUSE-SU-2024:14572-1 openSUSE-SU-2024:10600-1 openSUSE-SU-2024:10601-1 openSUSE-SU-2020:0366-1 openSUSE-SU-2020:0340-1

firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 74.0-r0
mozjs68 Alpine 3.12 68.6.0-r0
librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 74.0-r0
firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +10 more 68.6.0-r0
thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 68.6.0-r0

alpine advisories ALPINE-CVE-2020-6814

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 74.0-1
thunderbird Arch Linux 68.6.0-1

arch linux advisories AVG-1112 AVG-1115

Is CVE-2020-6814 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2020-6814 updated 2026-11-04 cvss 9.8

Mozilla: Memory safety bugs fixed in Firefox 74 and Firefox ESR 68.6

Red Hat Enterprise Linux 5 firefox, thunderbird
affected: no fix planned “Out of support scope”
Red Hat Enterprise Linux AppStream (v. 8) firefox 68.6.0-1.el8_1, thunderbird 68.6.0-1.el8_1
fixed: vendor fix RHSA-2020:0820
Red Hat Enterprise Linux AppStream E4S (v. 8.0) firefox 68.6.0-1.el8_0, thunderbird 68.6.0-1.el8_0
fixed: vendor fix RHSA-2020:0819
Red Hat Enterprise Linux Client (v. 7) firefox 68.6.0-1.el7_7, thunderbird 68.6.0-1.el7_7 Red Hat Enterprise Linux Client Optional (v. 7) firefox 68.6.0-1.el7_7
fixed: vendor fix RHSA-2020:0815
Red Hat Enterprise Linux Desktop (v. 6) firefox 68.6.0-1.el6_10, thunderbird 68.6.0-1.el6_10 Red Hat Enterprise Linux Desktop Optional (v. 6) firefox 68.6.0-1.el6_10 Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox 68.6.0-1.el6_10 Red Hat Enterprise Linux Server (v. 6) firefox 68.6.0-1.el6_10
fixed: vendor fix RHSA-2020:0816
Red Hat Enterprise Linux Server (v. 7) firefox 68.6.0-1.el7_7
fixed: vendor fix RHSA-2020:0815
Red Hat Enterprise Linux Server Optional (v. 6) firefox 68.6.0-1.el6_10, thunderbird 68.6.0-1.el6_10
fixed: vendor fix RHSA-2020:0816
Red Hat Enterprise Linux Server Optional (v. 7) firefox 68.6.0-1.el7_7, thunderbird 68.6.0-1.el7_7
fixed: vendor fix RHSA-2020:0815

show 4 more

Red Hat Enterprise Linux Workstation (v. 6) firefox 68.6.0-1.el6_10, thunderbird 68.6.0-1.el6_10
fixed: vendor fix RHSA-2020:0816
Red Hat Enterprise Linux Workstation (v. 7) firefox 68.6.0-1.el7_7, thunderbird 68.6.0-1.el7_7
fixed: vendor fix RHSA-2020:0815
Red Hat Enterprise Linux Workstation Optional (v. 6) firefox 68.6.0-1.el6_10
fixed: vendor fix RHSA-2020:0816
Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 68.6.0-1.el7_7
fixed: vendor fix RHSA-2020:0815

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

1.87% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	7.5	AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

Mozilla Thunderbird
Mozilla Firefox
Mozilla Firefox ESR

Classification

Weakness

CWE-787 Out-of-bounds Write

References

usn.ubuntu.com /4328-1/
vendor-advisory, third-party-advisory
usn.ubuntu.com /4335-1/
vendor-advisory, third-party-advisory
mozilla.org /security/advisories/mfsa2020-08/
vendor-advisory
mozilla.org /security/advisories/mfsa2020-10/
vendor-advisory
mozilla.org /security/advisories/mfsa2020-09/
vendor-advisory
bugzilla.mozilla.org /buglist.cgi?bug_id=1592078%2C1604847%2C1608256%2C1612636%2C1614339
issue-tracking, vendor-advisory

Sources

CVE List CVE-2020-6814
NVD CVE-2020-6814

Fencer Intel 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.

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