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Fencer Vulns
critical 9.8

CVE-2021-43527 in the critical feed json

NSS (Network Security Services) versions prior to 3.73 or 3.68.1 ESR are vulnerable to a heap overflow when handling DER-encoded DSA or RSA…

published 2021-12-08 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-30456

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
17.6%
EPSS 17.6% chance of exploitation in 30 days, percentile 97%
public exploits
0
none known

Summary

NSS (Network Security Services) versions prior to 3.73 or 3.68.1 ESR are vulnerable to a heap overflow when handling DER-encoded DSA or RSA-PSS signatures. Applications using NSS for handling signatures encoded within CMS, S/MIME, PKCS \#7, or PKCS \#12 are likely to be impacted. Applications using NSS for certificate validation or other TLS, X.509, OCSP or CRL functionality may be impacted, depending on how they configure NSS. *Note: This vulnerability does NOT impact Mozilla Firefox.* However, email clients and PDF viewers that use NSS for signature verification, such as Thunderbird, LibreOffice, Evolution and Evince are believed to be impacted. This vulnerability affects NSS < 3.73 and NSS < 3.68.1.

Patch / fix

  • Mozilla NSS 3.68.1, 3.73
  • nss Debian 14, Debian 13, Debian 12 2:3.73-1

debian advisories DEBIAN-CVE-2021-43527

  • nss Ubuntu 18.04 LTS 2:3.35-2ubuntu2.13
  • nss Ubuntu 20.04 LTS 2:3.49.1-1ubuntu1.6
  • nss Ubuntu 22.04 LTS 2:3.68-1ubuntu2
  • thunderbird Ubuntu 18.04 LTS 1:78.14.0+build1-0ubuntu0.18.04.2
  • thunderbird Ubuntu 20.04 LTS 1:78.14.0+build1-0ubuntu0.20.04.2
  • thunderbird Ubuntu 22.04 LTS 1:91.4.0+build1.1-0ubuntu1
  • nss Ubuntu Pro 14.04 LTS 2:3.28.4-0ubuntu0.14.04.5+esm10
  • nss Ubuntu Pro 16.04 LTS 2:3.28.4-0ubuntu0.16.04.14+esm2

ubuntu advisories UBUNTU-CVE-2021-43527

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

  • redhat-virtualization-host RHEL 7 4.3.20-20211202.1.el7_9
  • redhat-virtualization-host-image-update RHEL 7 4.3.20-20211202.1.el7_9
  • redhat-virtualization-host rhev hypervisor 4.4 4.4.9-202112061811_8.5
  • redhat-virtualization-host-image-update rhev hypervisor 4.4 4.4.9-202112061811_8.5
  • nss RHEL 8 3.67.0-7.el8_5
  • nss-util RHEL 8 3.67.0-7.el8_5
  • nss-tools RHEL 8 3.67.0-7.el8_5
  • nss-softokn RHEL 8 3.67.0-7.el8_5

red hat advisories RHSA-2021:4954RHSA-2021:4953RHSA-2021:4933RHSA-2021:5035RHSA-2021:4932RHSA-2021:5006

  • dtb-aarch64 openSUSE Leap 15.5 5.14.21-150500.55.68.1
  • kernel-64kb SLE Module for Basesystem 15 SP5, openSUSE Leap 15.5 5.14.21-150500.55.68.1
  • kernel-syms SLE Module for Development Tools 15 SP5, openSUSE Leap 15.5 5.14.21-150500.55.68.1
  • kernel-obs-qa openSUSE Leap 15.5 5.14.21-150500.55.68.1
  • kernel-source SLE Module for Development Tools 15 SP5, SLE Module for Basesystem 15 SP5, openSUSE Leap 15.5 5.14.21-150500.55.68.1
  • kernel-default SLE Workstation Extension 15 SP5, SLE Module for Legacy 15 SP5, SLE Module for Basesystem 15 SP5 +4 more 5.14.21-150500.55.68.1
  • kernel-kvmsmall openSUSE Leap 15.5 5.14.21-150500.55.68.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP5, openSUSE Leap 15.5 5.14.21-150500.55.68.1

suse advisories SUSE-SU-2025:02334-1SUSE-SU-2024:2190-1SUSE-SU-2024:2189-1SUSE-SU-2024:2185-1SUSE-SU-2024:2183-1SUSE-SU-2024:2019-1

  • mozilla-nss openSUSE Tumbleweed 3.73-1.1
  • mozilla-nss openSUSE Leap 15.3 3.68.1-3.61.1

opensuse advisories openSUSE-SU-2024:11663-1openSUSE-SU-2021:3934-1

  • nss AlmaLinux 8 3.67.0-7.el8_5
  • nss-util AlmaLinux 8 3.67.0-7.el8_5
  • nss-tools AlmaLinux 8 3.67.0-7.el8_5
  • nss-softokn AlmaLinux 8 3.67.0-7.el8_5
  • nss-sysinit AlmaLinux 8 3.67.0-7.el8_5
  • nss-softokn-freebl AlmaLinux 8 3.67.0-7.el8_5

almalinux advisories ALSA-2021:4903

  • nss Rocky Linux 8 3.67.0-7.el8_5

rocky linux advisories RLSA-2021:4903

  • nss Alpine 3.12 3.60-r2
  • nss Alpine 3.14, Alpine 3.13 3.66-r0
  • nss Alpine 3.15 3.72-r1
  • nss Alpine 3.24, Alpine 3.23, Alpine 3.22 +6 more 3.73-r0

alpine advisories ALPINE-CVE-2021-43527

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 3.75-1

azure linux advisories AZL-7024

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

  • nss Arch Linux 3.73-1
  • lib32-nss Arch Linux 3.73-1

arch linux advisories AVG-2596AVG-2597

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-2021-43527 updated cvss 9.8

nss: Memory corruption in decodeECorDsaSignature with DSA signatures (and RSA-PSS)

  • Red Hat Enterprise Linux AppStream (v. 8) nss 3.67.0-7.el8_5, nss-util 3.67.0-7.el8_5, nss-tools 3.67.0-7.el8_5, nss-softokn 3.67.0-7.el8_5, nss-sysinit 3.67.0-7.el8_5, nss-softokn-freebl 3.67.0-7.el8_5
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4903
  • Red Hat Enterprise Linux AppStream E4S (v. 8.1) thunderbird 91.3.0-3.el8_1
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4969
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) nss 3.44.0-10.el8_1, nss-util 3.44.0-10.el8_1, nss-tools 3.44.0-10.el8_1, nss-softokn 3.44.0-10.el8_1, nss-sysinit 3.44.0-10.el8_1, nss-softokn-freebl 3.44.0-10.el8_1
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4953
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) nss 3.53.1-12.el8_2, nss-util 3.53.1-12.el8_2, nss-tools 3.53.1-12.el8_2, thunderbird 91.3.0-3.el8_2, nss-softokn 3.53.1-12.el8_2, nss-sysinit 3.53.1-12.el8_2, +1 more
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4919
  • Red Hat Enterprise Linux AppStream EUS (v.8.4) nss 3.67.0-7.el8_4, nss-util 3.67.0-7.el8_4, nss-tools 3.67.0-7.el8_4, nss-softokn 3.67.0-7.el8_4, nss-sysinit 3.67.0-7.el8_4, nss-softokn-freebl 3.67.0-7.el8_4
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4909
  • Red Hat Enterprise Linux Client (v. 7) nss 3.67.0-4.el7_9, nss-tools 3.67.0-4.el7_9, nss-sysinit 3.67.0-4.el7_9 Red Hat Enterprise Linux Client Optional (v. 7) nss-devel 3.67.0-4.el7_9, nss-debuginfo 3.67.0-4.el7_9, nss-pkcs11-devel 3.67.0-4.el7_9 Red Hat Enterprise Linux ComputeNode Optional (v. 7) nss-devel 3.67.0-4.el7_9, nss-debuginfo 3.67.0-4.el7_9, nss-pkcs11-devel 3.67.0-4.el7_9
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4904
  • Red Hat Enterprise Linux Server (v. 6 ELS) nss 3.44.0-12.el6_10, nss-tools 3.44.0-12.el6_10, nss-sysinit 3.44.0-12.el6_10
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4907
  • Red Hat Enterprise Linux Server (v. 7) nss 3.67.0-4.el7_9, nss-tools 3.67.0-4.el7_9, nss-sysinit 3.67.0-4.el7_9
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4904
show 23 more
  • Red Hat Enterprise Linux Server AUS (v. 7.3) nss 3.28.4-2.el7_3, nss-tools 3.28.4-2.el7_3, nss-sysinit 3.28.4-2.el7_3
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4994
  • Red Hat Enterprise Linux Server AUS (v. 7.4) nss 3.28.4-18.el7_4, nss-tools 3.28.4-18.el7_4, nss-sysinit 3.28.4-18.el7_4
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4932
  • Red Hat Enterprise Linux Server AUS (v. 7.6) nss 3.36.0-10.2.el7_6, nss-tools 3.36.0-10.2.el7_6, nss-sysinit 3.36.0-10.2.el7_6
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4933
  • Red Hat Enterprise Linux Server AUS (v. 7.7) nss 3.44.0-8.el7_7, nss-tools 3.44.0-8.el7_7, nss-sysinit 3.44.0-8.el7_7
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4946
  • Red Hat Enterprise Linux Server E4S (v. 7.6) nss 3.36.0-10.2.el7_6, nss-tools 3.36.0-10.2.el7_6, nss-sysinit 3.36.0-10.2.el7_6
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4933
  • Red Hat Enterprise Linux Server E4S (v. 7.7) nss 3.44.0-8.el7_7, nss-tools 3.44.0-8.el7_7, nss-sysinit 3.44.0-8.el7_7
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4946
  • Red Hat Enterprise Linux Server Optional (v. 6 ELS) nss-debuginfo 3.44.0-12.el6_10, nss-pkcs11-devel 3.44.0-12.el6_10
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4907
  • Red Hat Enterprise Linux Server Optional (v. 7) nss-debuginfo 3.67.0-4.el7_9, nss-pkcs11-devel 3.67.0-4.el7_9
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4904
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.3) nss-debuginfo 3.28.4-2.el7_3, nss-pkcs11-devel 3.28.4-2.el7_3
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4994
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.4) nss-debuginfo 3.28.4-18.el7_4, nss-pkcs11-devel 3.28.4-18.el7_4
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4932
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.6) nss-debuginfo 3.36.0-10.2.el7_6, nss-pkcs11-devel 3.36.0-10.2.el7_6
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4933
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.7) nss-debuginfo 3.44.0-8.el7_7, nss-pkcs11-devel 3.44.0-8.el7_7
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4946
  • Red Hat Enterprise Linux Server Optional E4S (v. 7.6) nss-debuginfo 3.36.0-10.2.el7_6, nss-pkcs11-devel 3.36.0-10.2.el7_6
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4933
  • Red Hat Enterprise Linux Server Optional E4S (v. 7.7) nss-debuginfo 3.44.0-8.el7_7, nss-pkcs11-devel 3.44.0-8.el7_7
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4946
  • Red Hat Enterprise Linux Server Optional TUS (v. 7.6) nss-debuginfo 3.36.0-10.2.el7_6, nss-pkcs11-devel 3.36.0-10.2.el7_6
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4933
  • Red Hat Enterprise Linux Server Optional TUS (v. 7.7) nss-debuginfo 3.44.0-8.el7_7, nss-pkcs11-devel 3.44.0-8.el7_7
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4946
  • Red Hat Enterprise Linux Server TUS (v. 7.6) nss 3.36.0-10.2.el7_6, nss-tools 3.36.0-10.2.el7_6, nss-sysinit 3.36.0-10.2.el7_6
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4933
  • Red Hat Enterprise Linux Server TUS (v. 7.7) nss 3.44.0-8.el7_7, nss-tools 3.44.0-8.el7_7, nss-sysinit 3.44.0-8.el7_7
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4946
  • Red Hat Enterprise Linux Workstation (v. 7) nss 3.67.0-4.el7_9, nss-tools 3.67.0-4.el7_9, nss-sysinit 3.67.0-4.el7_9 Red Hat Enterprise Linux Workstation Optional (v. 7) nss-debuginfo 3.67.0-4.el7_9, nss-pkcs11-devel 3.67.0-4.el7_9
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:4904
  • Red Hat Virtualization 4 Hypervisor for RHEL 7 redhat-virtualization-host 4.3.20-20211202.1.el7_9, redhat-virtualization-host-image-update 4.3.20-20211202.1.el7_9
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:5035
  • Red Hat Virtualization 4 Hypervisor for RHEL 8 redhat-virtualization-host 4.4.9-202112061811_8.5, redhat-virtualization-host-image-update 4.4.9-202112061811_8.5
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:5006
  • Red Hat RHEL 7-based RHEV-H for RHEV 4 (build requirements) redhat-virtualization-host 4.3.20-20211202.1.el7_9, redhat-virtualization-host-image-update 4.3.20-20211202.1.el7_9
    fixed: vendor fix “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.” RHSA-2021:5035
  • Red Hat Enterprise Linux 6 thunderbird Red Hat Enterprise Linux 7 firefox, thunderbird Red Hat Enterprise Linux 8 firefox, thunderbird Red Hat Enterprise Linux 9 nss, nspr, firefox, nss-util, nss-tools, firefox-x11, +4 more Red Hat RHEL 7-based RHEV-H for RHEV 4 (build requirements) redhat-release-virtualization-host 4.3.20-1.el7ev, redhat-virtualization-host-image-update-placeholder 4.3.20-1.el7ev Red Hat RHEL 8-based RHEV-H for RHEV 4 (build requirements) redhat-release-virtualization-host 4.4.9-3.el8ev, redhat-release-virtualization-host-content 4.4.9-3.el8ev, redhat-virtualization-host-image-update-placeholder 4.4.9-3.el8ev
    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

cisa ICSA-24-102-04 updated cvss 9.8

Siemens RUGGEDCOM APE1808

  • Siemens RUGGEDCOM APE1808
    affected: vendor fix

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

17.56% chance of exploitation in the next 30 days, higher than 97% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Mozilla 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.