CVE-2020-12421

Name: CVE-2020-12421
Creator: NVD / NIST
Published: 2020-07-09T15:15:12.053+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.84%

Last modified Jun 17, 2026

CVE-2020-12421 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. When performing add-on updates, certificate chains terminating in non-built-in-roots were rejected (even if they were legitimately added by an administrator.) This could have caused add-ons to become out-of-date silently without notification to the user. This vulnerability affects Firefox ESR < 68.10, Firefox < 78, and Thunderbird < 68.10.0.. EPSS estimates a 1.84% chance of exploitation in the next 30 days.

Description

When performing add-on updates, certificate chains terminating in non-built-in-roots were rejected (even if they were legitimately added by an administrator.) This could have caused add-ons to become out-of-date silently without notification to the user. This vulnerability affects Firefox ESR < 68.10, Firefox < 78, and Thunderbird < 68.10.0.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.84%

76.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-295

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 78.0
Mozilla	Firefox Esr	< 68.10.0
Mozilla	Thunderbird	< 68.10.0
Canonical	Ubuntu Linux	16.04
Canonical	Ubuntu Linux	18.04
Canonical	Ubuntu Linux	19.10
Canonical	Ubuntu Linux	20.04

References

http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00023.htmlBroken Link
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00026.htmlBroken Link
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.htmlBroken Link
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.htmlBroken Link
https://bugzilla.mozilla.org/show_bug.cgi?id=1308251Issue Tracking, Vendor Advisory
https://security.gentoo.org/glsa/202007-09Third Party Advisory
https://security.gentoo.org/glsa/202007-10Third Party Advisory
https://usn.ubuntu.com/4421-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-24/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-25/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-26/Vendor Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00023.htmlBroken Link
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00026.htmlBroken Link
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.htmlBroken Link
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.htmlBroken Link
https://bugzilla.mozilla.org/show_bug.cgi?id=1308251Issue Tracking, Vendor Advisory
https://security.gentoo.org/glsa/202007-09Third Party Advisory
https://security.gentoo.org/glsa/202007-10Third Party Advisory
https://usn.ubuntu.com/4421-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-24/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-25/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-26/Vendor Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2020-12421?

How severe is CVE-2020-12421?

CVE-2020-12421 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.84% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12421?

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-2020-12421?

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

Scan your code now

Source: NVD / NIST