critical 9.8

CVE-2020-12395 json

Mozilla developers and community members reported memory safety bugs present in Firefox 75 and Firefox ESR 68.7.

published 2020-05-26 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4707

cvss: 9.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 2.6%; EPSS 2.6% chance of exploitation in 30 days, percentile 85%
public exploits: 0; none known

Mozilla developers and community members reported memory safety bugs present in Firefox 75 and Firefox ESR 68.7. 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 Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.

Patch / fix

fixed in 3 distros 7

Mozilla Firefox ESR 68.8
Mozilla Firefox 76
Mozilla Thunderbird 68.8.0

debian ubuntu red hat suse opensuse alpine arch linux

firefox-esr Debian 14, Debian 13, Debian 12 68.8.0esr-1
thunderbird Debian 14, Debian 13, Debian 12 1:68.8.0-1

debian advisories DEBIAN-CVE-2020-12395

firefox Ubuntu 16.04 LTS 76.0+build2-0ubuntu0.16.04.1
firefox Ubuntu 18.04 LTS 76.0+build2-0ubuntu0.18.04.1
firefox Ubuntu 20.04 LTS 76.0+build2-0ubuntu0.20.04.1
thunderbird Ubuntu 16.04 LTS 1:68.8.0+build2-0ubuntu0.16.04.2
thunderbird Ubuntu 18.04 LTS 1:68.8.0+build2-0ubuntu0.18.04.2
thunderbird Ubuntu 20.04 LTS 1:68.8.0+build2-0ubuntu0.20.04.2

ubuntu advisories UBUNTU-CVE-2020-12395

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 68.8.0-1.el7_8
thunderbird RHEL 8 68.8.0-1.el8_2
thunderbird RHEL 6 68.8.0-1.el6_10
firefox RHEL 7 68.8.0-1.el7_8
firefox RHEL 6 68.8.0-1.el6_10
firefox RHEL 8 68.8.0-1.el8_2
thunderbird RHEL 8.1 EUS 68.8.0-1.el8_1
thunderbird RHEL 8.0 E4S 68.8.0-1.el8_0

red hat advisories RHSA-2020:2050 RHSA-2020:2046 RHSA-2020:2049 RHSA-2020:2047 RHSA-2020:2048 RHSA-2020:2037

MozillaThunderbird SLE Workstation Extension 15 SP1 68.8.0-3.80.2
MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +16 more 68.8.0-109.119.1
MozillaFirefox SLE Module for Desktop Applications 15 SP1 68.8.0-3.87.1
MozillaFirefox SLES 11 SP4-LTSS 68.8.0-78.73.1

suse advisories SUSE-SU-2020:14359-1 SUSE-SU-2020:1225-1 SUSE-SU-2020:1218-1 SUSE-SU-2020:1209-1

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 68.8.0-lp151.2.38.2
MozillaFirefox openSUSE Leap 15.1 68.8.0-lp151.2.45.1

opensuse advisories openSUSE-SU-2024:14572-1 openSUSE-SU-2024:10600-1 openSUSE-SU-2024:10601-1 openSUSE-SU-2020:0643-1 openSUSE-SU-2020:0621-1

firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 76.0-r0
mozjs68 Alpine 3.12 68.8.0-r0
librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 76.0-r0
firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +10 more 68.8.0-r0
thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 68.8.0-r0

alpine advisories ALPINE-CVE-2020-12395

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 76.0-1
thunderbird Arch Linux 68.8.0-1

arch linux advisories AVG-1148 AVG-1155

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-2020-12395 updated 2026-11-04 cvss 9.8

Mozilla: Memory safety bugs fixed in Firefox 76 and Firefox ESR 68.8

Red Hat Enterprise Linux 5 firefox, thunderbird
affected: no fix planned “Out of support scope”
Red Hat Enterprise Linux AppStream (v. 8) firefox 68.8.0-1.el8_2, thunderbird 68.8.0-1.el8_2
fixed: vendor fix RHSA-2020:2031
Red Hat Enterprise Linux AppStream E4S (v. 8.0) firefox 68.8.0-1.el8_0, thunderbird 68.8.0-1.el8_0
fixed: vendor fix RHSA-2020:2033
Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox 68.8.0-1.el8_1, thunderbird 68.8.0-1.el8_1
fixed: vendor fix RHSA-2020:2032
Red Hat Enterprise Linux Client (v. 7) firefox 68.8.0-1.el7_8, thunderbird 68.8.0-1.el7_8 Red Hat Enterprise Linux Client Optional (v. 7) firefox 68.8.0-1.el7_8
fixed: vendor fix RHSA-2020:2037
Red Hat Enterprise Linux Desktop (v. 6) firefox 68.8.0-1.el6_10, thunderbird 68.8.0-1.el6_10 Red Hat Enterprise Linux Desktop Optional (v. 6) firefox 68.8.0-1.el6_10 Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox 68.8.0-1.el6_10 Red Hat Enterprise Linux Server (v. 6) firefox 68.8.0-1.el6_10
fixed: vendor fix RHSA-2020:2036
Red Hat Enterprise Linux Server (v. 7) firefox 68.8.0-1.el7_8
fixed: vendor fix RHSA-2020:2037
Red Hat Enterprise Linux Server Optional (v. 6) firefox 68.8.0-1.el6_10, thunderbird 68.8.0-1.el6_10
fixed: vendor fix RHSA-2020:2036

show 5 more

Red Hat Enterprise Linux Server Optional (v. 7) firefox 68.8.0-1.el7_8, thunderbird 68.8.0-1.el7_8
fixed: vendor fix RHSA-2020:2037
Red Hat Enterprise Linux Workstation (v. 6) firefox 68.8.0-1.el6_10, thunderbird 68.8.0-1.el6_10
fixed: vendor fix RHSA-2020:2036
Red Hat Enterprise Linux Workstation (v. 7) firefox 68.8.0-1.el7_8, thunderbird 68.8.0-1.el7_8
fixed: vendor fix RHSA-2020:2037
Red Hat Enterprise Linux Workstation Optional (v. 6) firefox 68.8.0-1.el6_10
fixed: vendor fix RHSA-2020:2036
Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 68.8.0-1.el7_8
fixed: vendor fix RHSA-2020:2037

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

2.60% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-08).

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	10.0	AV:N/AC:L/Au:N/C:C/I:C/A:C

Affected products

Mozilla Firefox ESR
Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-787 Out-of-bounds Write

References

usn.ubuntu.com /4373-1/
vendor-advisory, third-party-advisory
mozilla.org /security/advisories/mfsa2020-18/
vendor-advisory
mozilla.org /security/advisories/mfsa2020-16/
vendor-advisory
mozilla.org /security/advisories/mfsa2020-17/
vendor-advisory
bugzilla.mozilla.org /buglist.cgi?bug_id=1595886%2C1611482%2C1614704%2C1624098%2C1625749%2C1626382%2C1628076%2C1631508
broken-link, issue-tracking
security.gentoo.org /glsa/202005-03
third-party-advisory
security.gentoo.org /glsa/202005-04
third-party-advisory

Sources

CVE List CVE-2020-12395
NVD CVE-2020-12395

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.

Summary