CVE-2020-12387

Name: CVE-2020-12387
Creator: NVD / NIST
Published: 2020-05-26T18:15:10.98+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.1/10EPSS 1.40%

Last modified Jun 17, 2026

CVE-2020-12387 is a high-severity vulnerability rated 8.1/10 on the CVSS scale. A race condition when running shutdown code for Web Worker led to a use-after-free vulnerability. This resulted in a potentially exploitable crash. EPSS estimates a 1.40% chance of exploitation in the next 30 days.

Description

A race condition when running shutdown code for Web Worker led to a use-after-free vulnerability. This resulted in a potentially exploitable crash. This vulnerability affects Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.

Metrics

CVSS 3.1

8.1/10

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

EPSS Probability

1.40%

69.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 76.0
Mozilla	Firefox Esr	< 68.8.0
Mozilla	Thunderbird	< 68.8.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1545345Issue Tracking, Permissions Required
https://security.gentoo.org/glsa/202005-03Third Party Advisory
https://security.gentoo.org/glsa/202005-04Third Party Advisory
https://usn.ubuntu.com/4373-1/Broken Link
https://www.mozilla.org/security/advisories/mfsa2020-16/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-17/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-18/Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1545345Issue Tracking, Permissions Required
https://security.gentoo.org/glsa/202005-03Third Party Advisory
https://security.gentoo.org/glsa/202005-04Third Party Advisory
https://usn.ubuntu.com/4373-1/Broken Link
https://www.mozilla.org/security/advisories/mfsa2020-16/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-17/Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2020-18/Third Party Advisory

Timeline

Published: May 26, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-12387?

How severe is CVE-2020-12387?

CVE-2020-12387 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 1.40% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12387?

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-2020-12387?

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

Scan your code now

Source: NVD / NIST