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Fencer Vulns
critical 9.1

CVE-2020-12403 json

A flaw was found in the way CHACHA20-POLY1305 was implemented in NSS in versions before 3.55.

published 2021-05-27 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4715

cvss
9.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 75%
public exploits
0
none known

Summary

A flaw was found in the way CHACHA20-POLY1305 was implemented in NSS in versions before 3.55. When using multi-part Chacha20, it could cause out-of-bounds reads. This issue was fixed by explicitly disabling multi-part ChaCha20 (which was not functioning correctly) and strictly enforcing tag length. The highest threat from this vulnerability is to confidentiality and system availability.

Patch / fix

  • mozilla nss 3.55
  • nss Debian 14, Debian 13, Debian 12 2:3.55-1

debian advisories DEBIAN-CVE-2020-12403

  • nss Ubuntu 16.04 LTS 2:3.28.4-0ubuntu0.16.04.14
  • nss Ubuntu 18.04 LTS 2:3.35-2ubuntu2.12
  • nss Ubuntu 20.04 LTS 2:3.49.1-1ubuntu1.5
  • nss Ubuntu Pro 14.04 LTS 2:3.28.4-0ubuntu0.14.04.5+esm8

ubuntu advisories UBUNTU-CVE-2020-12403

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 3.53.1-17.el8_3
  • nss-util RHEL 8 3.53.1-17.el8_3
  • nss-tools RHEL 8 3.53.1-17.el8_3
  • nss-softokn RHEL 8 3.53.1-17.el8_3
  • nss-sysinit RHEL 8 3.53.1-17.el8_3
  • nss-softokn-freebl RHEL 8 3.53.1-17.el8_3
  • nss RHEL 7 3.53.1-3.el7_9
  • nspr RHEL 7 4.25.0-2.el7_9

red hat advisories RHSA-2021:1026RHSA-2021:0876RHSA-2021:0758RHSA-2021:0538RHSA-2020:4076

  • mozilla-nss SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 3.68-47.16.1
  • mozilla-nspr SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 4.32-33.6.1
  • mozilla-nss SLES 15 SP1-BCL, SLE Module for Server Applications 15 SP3, SLE Module for Server Applications 15 SP2 +16 more 3.68-3.56.1
  • mozilla-nspr SLES 15 SP1-BCL, SLE Module for Basesystem 15 SP3, SLE Module for Basesystem 15 SP2 +14 more 4.32-3.20.1
  • mozilla-nss SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 3.68-58.54.1
  • mozilla-nspr SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +11 more 4.32-19.18.1

suse advisories SUSE-RU-2021:14818-1SUSE-RU-2021:3115-2SUSE-RU-2021:3116-1SUSE-RU-2021:3115-1

  • mozilla-nss openSUSE Tumbleweed 3.69.1-1.2

opensuse advisories openSUSE-SU-2024:11058-1

  • nss Rocky Linux 8 3.53.1-17.el8_3

rocky linux advisories RLSA-2021:0538

  • nss Alpine 3.24, Alpine 3.23, Alpine 3.22 +10 more 3.55-r0

alpine advisories ALPINE-CVE-2020-12403

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

  • nss CBL-Mariner 2.0 3.44-10

azure linux advisories AZL-6746

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2020-12403 updated cvss 7.4

nss: CHACHA20-POLY1305 decryption with undersized tag leads to out-of-bounds read

  • Red Hat Enterprise Linux 5 nss Red Hat Enterprise Linux 6 nss, nss-tools, nss-sysinit
    affected: no fix planned “Out of support scope”
  • Red Hat OpenShift Do 1 openshiftdo/odo-init-image-rhel7 1.1.3-2
    fixed: vendor fix RHSA-2021:0949
  • Red Hat Enterprise Linux AppStream (v. 8) nss 3.53.1-17.el8_3, nss-util 3.53.1-17.el8_3, nss-tools 3.53.1-17.el8_3, nss-softokn 3.53.1-17.el8_3, nss-sysinit 3.53.1-17.el8_3, nss-softokn-freebl 3.53.1-17.el8_3
    fixed: vendor fix RHSA-2021:0538
  • Red Hat Enterprise Linux Client (v. 7) nss 3.53.1-3.el7_9, nspr 4.25.0-2.el7_9, nss-util 3.53.1-1.el7_9, nss-tools 3.53.1-3.el7_9, nss-softokn 3.53.1-6.el7_9, nss-sysinit 3.53.1-3.el7_9, +1 more Red Hat Enterprise Linux Client Optional (v. 7) nss-devel 3.53.1-3.el7_9, nspr-devel 4.25.0-2.el7_9, nss-debuginfo 3.53.1-3.el7_9, nspr-debuginfo 4.25.0-2.el7_9, nss-util-devel 3.53.1-1.el7_9, nss-pkcs11-devel 3.53.1-3.el7_9, +4 more
    fixed: vendor fix RHSA-2020:4076
  • Red Hat Enterprise Linux ComputeNode EUS (v. 7.6) nss 3.36.0-9.el7_6, nss-tools 3.36.0-9.el7_6, nss-softokn 3.36.0-7.el7_6, nss-sysinit 3.36.0-9.el7_6, nss-softokn-freebl 3.36.0-7.el7_6
    fixed: vendor fix RHSA-2021:0876
  • Red Hat Enterprise Linux ComputeNode EUS (v. 7.7) nss-softokn 3.44.0-9.el7_7, nss-softokn-freebl 3.44.0-9.el7_7
    fixed: vendor fix RHSA-2021:1026
  • Red Hat Enterprise Linux ComputeNode Optional (v. 7) nss-devel 3.53.1-3.el7_9, nspr-devel 4.25.0-2.el7_9, nss-debuginfo 3.53.1-3.el7_9, nspr-debuginfo 4.25.0-2.el7_9, nss-util-devel 3.53.1-1.el7_9, nss-pkcs11-devel 3.53.1-3.el7_9, +4 more
    fixed: vendor fix RHSA-2020:4076
  • Red Hat Enterprise Linux ComputeNode Optional EUS (v. 7.6) nss-devel 3.36.0-9.el7_6, nss-debuginfo 3.36.0-9.el7_6, nss-pkcs11-devel 3.36.0-9.el7_6, nss-softokn-devel 3.36.0-7.el7_6, nss-softokn-debuginfo 3.36.0-7.el7_6, nss-softokn-freebl-devel 3.36.0-7.el7_6
    fixed: vendor fix RHSA-2021:0876
show 10 more
  • Red Hat Enterprise Linux ComputeNode Optional EUS (v. 7.7) nss-softokn-devel 3.44.0-9.el7_7, nss-softokn-debuginfo 3.44.0-9.el7_7, nss-softokn-freebl-devel 3.44.0-9.el7_7
    fixed: vendor fix RHSA-2021:1026
  • Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server (v. 7) nss 3.36.0-9.el7_6, nss-tools 3.36.0-9.el7_6, nss-softokn 3.36.0-7.el7_6, nss-sysinit 3.36.0-9.el7_6, nss-softokn-freebl 3.36.0-7.el7_6 Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server Optional (v. 7) nss-debuginfo 3.36.0-9.el7_6, nss-pkcs11-devel 3.36.0-9.el7_6
    fixed: vendor fix RHSA-2021:0876
  • Red Hat Enterprise Linux Server (v. 7) nss 3.53.1-3.el7_9, nspr 4.25.0-2.el7_9, nss-util 3.53.1-1.el7_9, nss-tools 3.53.1-3.el7_9, nss-softokn 3.53.1-6.el7_9, nss-sysinit 3.53.1-3.el7_9, +1 more
    fixed: vendor fix RHSA-2020:4076
  • Red Hat Enterprise Linux Server AUS (v. 7.4) nss-softokn 3.28.3-10.el7_4, nss-softokn-freebl 3.28.3-10.el7_4 Red Hat Enterprise Linux Server E4S (v. 7.4) nss-softokn 3.28.3-10.el7_4, nss-softokn-freebl 3.28.3-10.el7_4
    fixed: vendor fix RHSA-2021:0758
  • Red Hat Enterprise Linux Server EUS (v. 7.6) nss 3.36.0-9.el7_6, nss-tools 3.36.0-9.el7_6, nss-softokn 3.36.0-7.el7_6, nss-sysinit 3.36.0-9.el7_6, nss-softokn-freebl 3.36.0-7.el7_6
    fixed: vendor fix RHSA-2021:0876
  • Red Hat Enterprise Linux Server EUS (v. 7.7) nss-softokn 3.44.0-9.el7_7, nss-softokn-freebl 3.44.0-9.el7_7
    fixed: vendor fix RHSA-2021:1026
  • Red Hat Enterprise Linux Server Optional (v. 7) nss-debuginfo 3.53.1-3.el7_9, nss-pkcs11-devel 3.53.1-3.el7_9
    fixed: vendor fix RHSA-2020:4076
  • Red Hat Enterprise Linux Server Optional EUS (v. 7.6) nss-debuginfo 3.36.0-9.el7_6, nss-pkcs11-devel 3.36.0-9.el7_6
    fixed: vendor fix RHSA-2021:0876
  • Red Hat Enterprise Linux Server TUS (v. 7.4) nss-softokn 3.28.3-10.el7_4, nss-softokn-freebl 3.28.3-10.el7_4
    fixed: vendor fix RHSA-2021:0758
  • Red Hat Enterprise Linux Workstation (v. 7) nss 3.53.1-3.el7_9, nspr 4.25.0-2.el7_9, nss-util 3.53.1-1.el7_9, nss-tools 3.53.1-3.el7_9, nss-softokn 3.53.1-6.el7_9, nss-sysinit 3.53.1-3.el7_9, +1 more Red Hat Enterprise Linux Workstation Optional (v. 7) nss-debuginfo 3.53.1-3.el7_9, nss-pkcs11-devel 3.53.1-3.el7_9
    fixed: vendor fix RHSA-2020:4076

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

1.54% chance of exploitation in the next 30 days, higher than 75% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
NVD 2.0 6.4 AV:N/AC:L/Au:N/C:P/I:N/A:P

Affected products

  • n/a nss

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.