← Vulnerability feed

Vulnerability record · CVE-2021-4209 · published 24 August 2022

CVE-2021-4209: Gnutls null pointer dereference vulnerability

Gnu · Gnutls

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.

6.5 CVSS 3.1 Medium EPSS 1.7% · top 23.1% CWE-476 · NULL pointer dereference
6.5CVSS 3.1 base score
1.7%EPSS exploitation probability, 30 days
NoNot in CISA KEV
5Affected product versions listed by NVD
12References
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

5 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://access.redhat.com/security/cve/CVE-2021-4209 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2044156 Issue TrackingThird Party Advisory
https://gitlab.com/gnutls/gnutls/-/commit/3db352734472d851318944db13be73da61300568 PatchThird 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
https://access.redhat.com/security/cve/CVE-2021-4209 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2044156 Issue TrackingThird Party Advisory
https://gitlab.com/gnutls/gnutls/-/commit/3db352734472d851318944db13be73da61300568 PatchThird 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

Track CVE-2021-4209 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2021-44228Apache Log4j2 JNDI lookup remote code executionApache Log4j2 versions 2.0-beta9 through 2.15.0 (excluding 2.12.2, 2.12.3, and 2.3.1) do not protect against attacker-controlled LDAP and other JNDI …KEVEPSS 100%analysed9.8CVE-2019-11043PHP-FPM buffer overflow enables remote code executionPHP-FPM in certain configurations writes past allocated buffers into FCGI protocol data space, an out-of-bounds write (CWE-787, CWE-120). It affects …KEVEPSS 100%analysed9.8CVE-2018-14667RichFaces Framework EL injection enables unauthenticated remote code executionRichFaces Framework 3.X through 3.3.4 is vulnerable to Expression Language injection through the UserResource resource. A remote, unauthenticated att…KEVEPSS 74%analysed9.8CVE-2014-7169GNU Bash environment variable function parsing command injection (Shellshock variant)GNU Bash through 4.3 bash43-025 processes trailing strings after malformed function definitions in environment variable values, allowing command inje…KEVEPSS 100%analysed9.8CVE-2014-6271GNU Bash environment variable command injection (ShellShock)GNU Bash through 4.3 processes trailing strings after function definitions in environment variable values, allowing injected commands to run when Bas…KEVEPSS 100%analysed9.0CVE-2021-40438Apache HTTP Server mod_proxy SSRF via crafted URI pathA crafted request URI path can make mod_proxy forward the request to an origin server chosen by the remote user, an SSRF flaw in Apache HTTP Server 2…KEVEPSS 100%analysed8.8CVE-2025-31277Apple WebKit memory corruption via malicious web contentApple WebKit fails to handle memory correctly when processing crafted web content, leading to memory corruption across Safari, iOS, iPadOS, macOS, tv…KEVEPSS 1.6%analysed8.8CVE-2023-5217libvpx VP8 encoding heap buffer overflow exploited via crafted HTMLA heap buffer overflow in the VP8 encoder in libvpx affects Google Chrome before 117.0.5938.132 and libvpx 1.13.1, and is reachable through a crafted…KEVEPSS 49%analysed

Source: NIST National Vulnerability Database (record CVE-2021-4209), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.