CVE-2020-12420

Name: CVE-2020-12420
Creator: NVD / NIST
Published: 2020-07-09T15:15:11.973+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.8/10EPSS 1.86%

Last modified Jun 17, 2026

CVE-2020-12420 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. When trying to connect to a STUN server, a race condition could have caused a use-after-free of a pointer, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox ESR < 68.10, Firefox < 78, and Thunderbird < 68.10.0.. EPSS estimates a 1.86% chance of exploitation in the next 30 days.

Description

When trying to connect to a STUN server, a race condition could have caused a use-after-free of a pointer, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox ESR < 68.10, Firefox < 78, and Thunderbird < 68.10.0.

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

1.86%

76.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

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
Opensuse	Leap	15.1
Opensuse	Leap	15.2

References

http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00023.htmlMailing List, Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00026.htmlMailing List, Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.htmlMailing List, Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.htmlMailing List, Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1643437Exploit, Issue 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.htmlMailing List, Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00026.htmlMailing List, Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00027.htmlMailing List, Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00049.htmlMailing List, Third Party Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1643437Exploit, Issue 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-2020-12420?

How severe is CVE-2020-12420?

CVE-2020-12420 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 1.86% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12420?

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-2020-12420?

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

Scan your code now

Source: NVD / NIST