CVE-2020-12399

Name: CVE-2020-12399
Creator: NVD / NIST
Published: 2020-07-09T15:15:10.757+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.4/10EPSS 0.65%

Last modified Jun 17, 2026

CVE-2020-12399 is a medium-severity vulnerability rated 4.4/10 on the CVSS scale. NSS has shown timing differences when performing DSA signatures, which was exploitable and could eventually leak private keys. This vulnerability affects Thunderbird < 68.9.0, Firefox < 77, and Firefox ESR < 68.9.. EPSS estimates a 0.65% chance of exploitation in the next 30 days.

Description

NSS has shown timing differences when performing DSA signatures, which was exploitable and could eventually leak private keys. This vulnerability affects Thunderbird < 68.9.0, Firefox < 77, and Firefox ESR < 68.9.

Metrics

CVSS 3.1

4.4/10

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

EPSS Probability

0.65%

46.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-203

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 77.0
Mozilla	Firefox Esr	< 68.9.0
Mozilla	Thunderbird	< 68.9.0
Debian	Debian Linux	9.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1631576Issue Tracking, Permissions Required, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2020/09/msg00029.htmlMailing List, Third Party Advisory
https://security.gentoo.org/glsa/202007-49Third Party Advisory
https://usn.ubuntu.com/4421-1/Third Party Advisory
https://www.debian.org/security/2020/dsa-4726Third 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=1631576Issue Tracking, Permissions Required, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2020/09/msg00029.htmlMailing List, Third Party Advisory
https://security.gentoo.org/glsa/202007-49Third Party Advisory
https://usn.ubuntu.com/4421-1/Third Party Advisory
https://www.debian.org/security/2020/dsa-4726Third 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-2020-12399?

How severe is CVE-2020-12399?

CVE-2020-12399 has a CVSS score of 4.4/10 (MEDIUM severity). The EPSS model estimates a 0.65% probability of exploitation in the next 30 days.

How do I fix CVE-2020-12399?

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-2020-12399?

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

Scan your code now

Source: NVD / NIST