CVE-2020-12399

Severity: medium (CVSS 4.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% 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-203

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.

Affected products

Debian Linux: 9.0
Mozilla Firefox: before 77.0 — fixed in 77.0
Mozilla Firefox ESR: before 68.9.0 — fixed in 68.9.0
Mozilla Thunderbird: before 68.9.0 — fixed in 68.9.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 77.0; Mozilla Firefox ESR 68.9.0; Mozilla Thunderbird 68.9.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1631576
https://lists.debian.org/debian-lts-announce/2020/09/msg00029.html
https://security.gentoo.org/glsa/202007-49
https://usn.ubuntu.com/4421-1/
https://www.debian.org/security/2020/dsa-4726
https://www.mozilla.org/security/advisories/mfsa2020-20/
https://www.mozilla.org/security/advisories/mfsa2020-21/
https://www.mozilla.org/security/advisories/mfsa2020-22/
https://bugzilla.mozilla.org/show_bug.cgi?id=1631576
https://lists.debian.org/debian-lts-announce/2020/09/msg00029.html
https://security.gentoo.org/glsa/202007-49
https://usn.ubuntu.com/4421-1/

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