CVE-2020-12406

Name: CVE-2020-12406
Creator: NVD / NIST
Published: 2020-07-09T15:15:11.02+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 1.02%

Last modified Jun 17, 2026

CVE-2020-12406 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. Mozilla Developer Iain Ireland discovered a missing type check during unboxed objects removal, resulting in a crash. We presume that with enough effort that it could be exploited to run arbitrary code. EPSS estimates a 1.02% chance of exploitation in the next 30 days.

Description

Mozilla Developer Iain Ireland discovered a missing type check during unboxed objects removal, resulting in a crash. We presume that with enough effort that it could be exploited to run arbitrary code. This vulnerability affects Thunderbird < 68.9.0, Firefox < 77, and Firefox ESR < 68.9.

Metrics

CVSS 3.1

8.8/10

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

EPSS Probability

1.02%

59.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-345

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 77.0
Mozilla	Firefox Esr	< 68.9.0
Mozilla	Thunderbird	< 68.9.0
Canonical	Ubuntu Linux	16.04
Canonical	Ubuntu Linux	18.04
Canonical	Ubuntu Linux	19.10
Canonical	Ubuntu Linux	20.04

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1639590Issue Tracking, Vendor Advisory
https://usn.ubuntu.com/4421-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-20/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-21/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-22/Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1639590Issue Tracking, Vendor Advisory
https://usn.ubuntu.com/4421-1/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-20/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-21/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2020-22/Vendor Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2020-12406?

How severe is CVE-2020-12406?

CVE-2020-12406 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 1.02% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12406?

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-2020-12406?

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

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Source: NVD / NIST