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Fencer Vulns
medium 4.4

CVE-2020-12399 json

NSS has shown timing differences when performing DSA signatures, which was exploitable and could eventually leak private keys.

published 2020-07-09 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4711

cvss
4.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 51%
public exploits
0
none known

Summary

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.

Patch / fix

  • Mozilla Thunderbird 68.9.0
  • Mozilla Firefox 77
  • Mozilla Firefox ESR 68.9
  • nss Debian 14, Debian 13, Debian 12 2:3.53-1
  • firefox-esr Debian 14, Debian 13, Debian 12 68.9.0esr-1
  • thunderbird Debian 14, Debian 13, Debian 12 1:68.9.0-1

debian advisories DEBIAN-CVE-2020-12399

  • nss Ubuntu 16.04 LTS 2:3.28.4-0ubuntu0.16.04.11
  • nss Ubuntu 18.04 LTS 2:3.35-2ubuntu2.8
  • nss Ubuntu 20.04 LTS 2:3.49.1-1ubuntu1.1
  • firefox Ubuntu 16.04 LTS 77.0.1+build1-0ubuntu0.16.04.1
  • firefox Ubuntu 18.04 LTS 77.0.1+build1-0ubuntu0.18.04.1
  • firefox Ubuntu 20.04 LTS 77.0.1+build1-0ubuntu0.20.04.1
  • thunderbird Ubuntu 16.04 LTS 1:68.10.0+build1-0ubuntu0.16.04.1
  • thunderbird Ubuntu 18.04 LTS 1:68.10.0+build1-0ubuntu0.18.04.1

ubuntu advisories UBUNTU-CVE-2020-12399

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • nss RHEL 8 3.53.1-11.el8_2
  • nspr RHEL 8 4.25.0-2.el8_2
  • nss-util RHEL 8 3.53.1-11.el8_2
  • nss-tools RHEL 8 3.53.1-11.el8_2
  • nss-softokn RHEL 8 3.53.1-11.el8_2
  • nss-sysinit RHEL 8 3.53.1-11.el8_2
  • nss-softokn-freebl RHEL 8 3.53.1-11.el8_2

red hat advisories RHSA-2020:3280

  • mozilla-nss SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 3.53.1-58.48.1
  • mozilla-nspr SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 4.25-19.15.1
  • mozilla-nss SLES for SAP 15, SLES 15-LTSS, SLE Module for Server Applications 15 SP2 +5 more 3.53-3.40.1
  • mozilla-nspr SLES for SAP 15, SLES 15-LTSS, SLE Module for Basesystem 15 SP2 +3 more 4.25-3.12.1
  • mozilla-nss SLES 11 SP4-LTSS 3.53.1-38.23.1
  • mozilla-nspr SLES 11 SP4-LTSS 4.25-29.12.2

suse advisories SUSE-SU-2020:14418-1SUSE-SU-2020:1839-1SUSE-SU-2020:1677-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2
  • mozilla-nss openSUSE Tumbleweed 3.69.1-1.2
  • mozilla-nss openSUSE Leap 15.1 3.53-lp151.2.23.1
  • mozilla-nspr openSUSE Leap 15.1 4.25-lp151.2.9.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1openSUSE-SU-2024:11058-1openSUSE-SU-2020:0854-1

  • nspr Rocky Linux 8 4.25.0-2.el8_2

rocky linux advisories RLSA-2020:3280

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 77.0-r0
  • mozjs68 Alpine 3.12 68.9.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 77.0-r0
  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +10 more 68.9.0-r0
  • thunderbird Alpine 3.23, Alpine 3.22, Alpine 3.21 +5 more 68.9.0-r0

alpine advisories ALPINE-CVE-2020-12399

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • firefox Arch Linux 77.0-1
  • thunderbird Arch Linux 68.9.0-1

arch linux advisories AVG-1173AVG-1179

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-12399 updated cvss 4.4

nss: Timing attack on DSA signature generation

  • Red Hat Enterprise Linux 5 nss, firefox, thunderbird Red Hat Enterprise Linux 6 nss, nss-tools, nss-sysinit
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) nspr 4.25.0-2.el8_2, nss 3.53.1-11.el8_2, nss-util 3.53.1-11.el8_2, nss-tools 3.53.1-11.el8_2, nss-softokn 3.53.1-11.el8_2, nss-sysinit 3.53.1-11.el8_2, +1 more
    fixed: vendor fix RHSA-2020:3280
  • Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 nss, firefox, nss-tools, nss-sysinit, thunderbird Red Hat Enterprise Linux 8 firefox, thunderbird Red Hat OpenShift Container Platform 4 nss-altfiles
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.65% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 4.4 CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N
NVD 2.0 1.2 AV:L/AC:H/Au:N/C:P/I:N/A:N

Affected products

  • Mozilla Thunderbird
  • Mozilla Firefox
  • Mozilla Firefox ESR

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.