CVE-2021-43527

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2021-12-09. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Elevated
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 18%CVSS: 9.8Exploit: Elevated riskExposed: 0

A fix is available — apply it.

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.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
65(Track*)
EG Risk 65/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation40% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
18%
EPSS %ILE
97%
KEV
Not listed

Published

December 8, 2021

Last Modified

November 21, 2024

Advisory Details (8)

Auto-updated Sep 4, 2026
No patch confirmed yet.
generic

1737470 - (CVE-2021-43527) Memory Corruption in decodeECorDsaSignature with DSA signatures (and RSA-PSS)

https://bugzilla.mozilla.org/show_bug.cgi?id=1737470
generic

CVE-2021-43527 NSS heap overflow in StarWind products

https://www.starwindsoftware.com/security/sw-20220802-0001/
generic

Memory corruption in NSS via DER-encoded DSA and RSA-PSS signatures — Mozilla

https://www.mozilla.org/security/advisories/mfsa2021-51/
generic

NetApp Product Security

https://security.netapp.com/advisory/ntap-20211229-0002/
generic

Mozilla Network Security Service (NSS): Multiple Vulnerabilities (GLSA 202212-05) — Gentoo security

https://security.gentoo.org/glsa/202212-05
generic

Directory Listing: /pub/security/nss/releases/NSS_3_73_RTM/

https://ftp.mozilla.org/pub/security/nss/releases/NSS_3_73_RTM/
generic

Directory Listing: /pub/security/nss/releases/NSS_3_68_1_RTM/

https://ftp.mozilla.org/pub/security/nss/releases/NSS_3_68_1_RTM/
generic
https://cert-portal.siemens.com/productcert/pdf/ssa-594438.pdf

Vendor Advisories for CVE-2021-43527(6)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(18)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibnss3-tools (2:3.35-2ubuntu2.13) @ bionic2026-05-26ubuntu
ubuntulibnss3-tools (2:3.28.4-0ubuntu0.16.04.14+esm2) @ xenial2026-05-26ubuntu
ubuntulibnss3-tools (2:3.28.4-0ubuntu0.16.04.14+esm1) @ xenial2026-05-26ubuntu
ubuntuthunderbird-locale-id (1:78.14.0+build1-0ubuntu0.21.04.2) @ hirsute2026-05-26ubuntu
redhatredhat-virtualization-host-0:4.3.20-20211202.1.el7_92021-12-08redhat
redhatredhat-virtualization-host-0:4.4.9-202112061811_8.52021-12-08redhat
redhatnss-0:3.28.4-2.el7_32021-12-07redhat
redhatnss-0:3.28.4-18.el7_42021-12-06redhat
redhatnss-0:3.44.0-10.el8_12021-12-06redhat
redhatnss-0:3.36.0-10.2.el7_62021-12-06redhat
redhatnss-0:3.44.0-8.el7_72021-12-06redhat
redhatthunderbird-0:91.3.0-3.el8_12021-12-06redhat
redhatthunderbird-0:91.3.0-3.el8_22021-12-06redhat
redhatnss-0:3.53.1-12.el8_22021-12-02redhat
redhatnss-0:3.67.0-7.el8_42021-12-02redhat
redhatnss-0:3.67.0-7.el8_52021-12-01redhat
redhatnss-0:3.44.0-12.el6_102021-12-01redhat
redhatnss-0:3.67.0-4.el7_92021-12-01redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(13 across 13 ecosystems)
Alpine:v3.12(1)
PackageVulnerable rangeFixed inDependents
nss—3.60-r2—
Alpine:v3.19(1)
PackageVulnerable rangeFixed inDependents
nss—3.73-r0—
Alpine:v3.20(1)
PackageVulnerable rangeFixed inDependents
nss—3.73-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
nss—3.73-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
nss—3.73-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
nss—3.73-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
nss—3.73-r0—
Debian:10(1)
PackageVulnerable rangeFixed inDependents
nss2:3.42.1-1, 2:3.42.1-1+deb10u1, 2:3.42.1-1+deb10u2, 2:3.42.1-1+deb10u32:3.42.1-1+deb10u4—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
nss2:3.61-12:3.61-1+deb11u1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
nss—2:3.73-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
nss—2:3.73-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
nss—2:3.73-1—
Debian:9(1)
PackageVulnerable rangeFixed inDependents
nss2:3.26.2-1.1, 2:3.26.2-1.1+deb9u1, 2:3.26.2-1.1+deb9u22:3.26.2-1.1+deb9u3—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(13)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 7× in last 7d / 30× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 145 total refreshes for this CVE.

  1. 2026-09-07 15:58 UTCEPSS rescore
  2. 2026-09-06 13:45 UTCEPSS rescore
  3. 2026-09-06 02:00 UTCOSV refresh
  4. 2026-09-05 15:25 UTCEPSS rescore
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  23. 2026-08-19 13:29 UTCOSV refresh
  24. 2026-08-18 13:45 UTCEPSS rescore
  25. 2026-08-16 14:53 UTCEPSS rescore
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  1. 2026-08-16 02:11 UTCEPSS rescore
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  3. 2026-08-13 21:57 UTCEPSS rescore
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  8. 2026-08-06 13:44 UTCEPSS rescore
  9. 2026-08-05 19:14 UTCEPSS rescore
  10. 2026-08-04 10:34 UTCEPSS rescore
  11. 2026-08-04 09:27 UTCOSV refresh
  12. 2026-08-03 10:33 UTCEPSS rescore
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  21. 2026-07-23 02:05 UTCEG score recompute
  22. 2026-07-22 22:51 UTCEG score recompute
  23. 2026-07-22 14:06 UTCEPSS rescore
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  26. 2026-07-20 17:05 UTCEPSS rescore
  27. 2026-07-19 14:29 UTCEPSS rescore
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  31. 2026-07-18 06:29 UTCOSV refresh
  32. 2026-07-16 17:00 UTCEPSS rescore
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  45. 2026-07-08 15:12 UTCEPSS rescore
  46. 2026-07-07 13:43 UTCEPSS rescore
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  49. 2026-07-05 02:28 UTCEPSS rescore
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  55. 2026-06-30 03:00 UTCOSV refresh
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Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2021-43527?
CVE-2021-43527 is a critical vulnerability published on December 8, 2021. 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…
When was CVE-2021-43527 disclosed?
CVE-2021-43527 was first published in the National Vulnerability Database on December 8, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-43527 actively exploited?
CVE-2021-43527 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 18% probability of exploitation in the next 30 days, which ranks it in the top 3.1% of all scored CVEs.
What is the CVSS score of CVE-2021-43527?
CVE-2021-43527 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-43527?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-43527, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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