Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-4209

CVE-2021-4209MEDIUM

n/a GnuTLS — A NULL pointer dereference flaw was found in GnuTLS.

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   L   N  U  N  N  H    6.5   .0191   79.4     —

AFFECTED
  Product  Versions                  Fixed
  GnuTLS   Fixed in gnutls v3.7.3 –  —

TIMELINE
  Jan 24  Reserved by redhat
  Aug 24  Published (CNA: redhat)
  Oct 14  ENRICHED — CVE-2021-4209 (GnuTLS). Received CVSS 6.5 and CPE data from NVD.

CWE-476 · CNA: redhat · CVSS v3.1 · 7 references · NVD status: Modified

Description

A NULL pointer dereference flaw was found in GnuTLS. As Nettle's hash update functions internally call memcpy, providing zero-length input may cause undefined behavior. This flaw leads to a denial of service after authentication in rare circumstances.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
January 24, 2022	Reserved	Reserved by redhat
August 24, 2022	Published	Published (CNA: redhat)
October 14, 2026	ENRICHED	ENRICHED — CVE-2021-4209 (GnuTLS). Received CVSS 6.5 and CPE data from NVD.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
n/a	GnuTLS	—	Fixed in gnutls v3.7.3	—

Weaknesses

CWE-476

References (7)

https://access.redhat.com/security/cve/CVE-2021-4209 [Third Party Advisory]
https://bugzilla.redhat.com/show_bug.cgi?id=2044156 [Issue Tracking, Third Party Advisory]
https://cert-portal.siemens.com/productcert/html/ssa-398330.html
https://gitlab.com/gnutls/gnutls/-/commit/3db352734472d851318944db13be73da61300568 [Patch, Third Party Advisory]
https://gitlab.com/gnutls/gnutls/-/issues/1306 [Third Party Advisory]
https://gitlab.com/gnutls/gnutls/-/merge_requests/1503 [Third Party Advisory]
https://security.netapp.com/advisory/ntap-20220915-0005/ [Third Party Advisory]

Authoritative record: CVE-2021-4209 at cve.org

Weaknesses: CWE-476

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-4209 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.