---
id: CVE-2021-4209
title: A NULL pointer dereference flaw was found in GnuTLS
summary: >-
  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 …
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-476
  - CWE-476
vendor: gnu
product: gnutls
affected:
  - gnutls < 3.7.3
  - enterprise_linux = 8.0
  - active_iq_unified_manager
  - solidfire_&_hci_management_node
  - hci_bootstrap_os
patched:
  - gnutls 3.7.3
published: '2022-08-24'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T11:16:55.207'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2021-4209'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2021-4209'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2044156'
    label: secalert@redhat.com
  - url: >-
      https://gitlab.com/gnutls/gnutls/-/commit/3db352734472d851318944db13be73da61300568
    label: secalert@redhat.com
  - url: 'https://gitlab.com/gnutls/gnutls/-/issues/1306'
    label: secalert@redhat.com
  - url: 'https://gitlab.com/gnutls/gnutls/-/merge_requests/1503'
    label: secalert@redhat.com
  - url: 'https://security.netapp.com/advisory/ntap-20220915-0005/'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2021-4209'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2044156'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://gitlab.com/gnutls/gnutls/-/commit/3db352734472d851318944db13be73da61300568
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://gitlab.com/gnutls/gnutls/-/issues/1306'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://gitlab.com/gnutls/gnutls/-/merge_requests/1503'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20220915-0005/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-398330.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
epss: 0.01748
epssPercentile: 0.77253
ingestedAt: '2026-10-14T11:27:22.129Z'
---

## Overview

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.

## Affected

- `gnutls < 3.7.3`
- `enterprise_linux = 8.0`
- `active_iq_unified_manager`
- `solidfire_&_hci_management_node`
- `hci_bootstrap_os`

## Remediation

Upgrade past the affected range:

- `gnutls 3.7.3`