What’s Vulnerable › Vulnerabilities

CVE-2020-12421

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-07-09 · updated 2026-06-17
• Weakness: CWE-295

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 This could have caused add-ons to become out-of-date silently without notification to the user.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.

Affected products

• Canonical Ubuntu Linux: 16.04, 18.04, 19.10, 20.04
• Mozilla Firefox: before 78.0 — fixed in 78.0
• Mozilla Firefox ESR: before 68.10.0 — fixed in 68.10.0
• Mozilla Thunderbird: before 68.10.0 — fixed in 68.10.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 78.0; Mozilla Firefox ESR 68.10.0; Mozilla Thunderbird 68.10.0. Check the vendor advisory for mitigations.

References

• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00023.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00026.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.html
• https://bugzilla.mozilla.org/show_bug.cgi?id=1308251
• https://security.gentoo.org/glsa/202007-09
• https://security.gentoo.org/glsa/202007-10
• https://usn.ubuntu.com/4421-1/
• https://www.mozilla.org/security/advisories/mfsa2020-24/
• https://www.mozilla.org/security/advisories/mfsa2020-25/
• https://www.mozilla.org/security/advisories/mfsa2020-26/
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00023.html

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