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Vulnerabilities

Vulnerability · CVE-2021-4209

A NULL pointer dereference flaw was found in GnuTLS.

Published Aug 24, 2022 · catalog updated Oct 14, 2026 · A NULL pointer dereference

Check if you run it

No confirmed exploitation is on record for CVE-2021-4209. EPSS is 1.79%. Act only if a listed version of A NULL pointer dereference is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (A NULL pointer dereference).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
1.79%
Remediation
Advisory link
Affected products
cpe gnu/gnutls · cpe netapp/active iq unified manager · cpe netapp/hci bootstrap os · cpe netapp/solidfire & hci management node · cpe redhat/enterprise linux

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe gnu/gnutlsversion unspecified
  • cpe netapp/active iq unified managerversion unspecified
  • cpe netapp/hci bootstrap osversion unspecified
  • cpe netapp/solidfire & hci management nodeversion unspecified
  • cpe redhat/enterprise linux8.0

How to fix CVE-2021-4209

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2021-4209. EPSS is 1.79%. Act only if a listed version of A NULL pointer dereference is installed.

Which versions are affected?

Compare what you have installed with redhat/enterprise linux 8.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-476: NULL Pointer Dereference. EPSS 1.79%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Aug 24, 2022 · NIST NVD

    Detected

    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.

  2. Oct 14, 2026 · NIST NVD

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2021-4209

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-4209

    30-day exploitation probability 1.8%

    first.org
  • NIST NVDVulnerability recordCVE-2021-4209

    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.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 16, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.