MEDIUM
CVE-2021-4209
CWE-476Published: August 24, 2022· Updated: Jun 17, 2026
6.5
CVSS v3.1
Official 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.
Technical Analysis
CVE-2021-4209 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in availability disruption (denial of service), with a CVSS base score of 6.5.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Affected Vendors & Products
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.
Official Patches & Advisories
All References (12)
→
https://access.redhat.com/security/cve/CVE-2021-4209Third Party Advisory
→
https://bugzilla.redhat.com/show_bug.cgi?id=2044156Issue Tracking · Third Party Advisory
→
https://gitlab.com/gnutls/gnutls/-/commit/3db352734472d851318944db13be73da61300568Patch · Third Party Advisory
→
https://gitlab.com/gnutls/gnutls/-/issues/1306Third Party Advisory
→
https://gitlab.com/gnutls/gnutls/-/merge_requests/1503Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20220915-0005/Third Party Advisory
→
https://access.redhat.com/security/cve/CVE-2021-4209Third Party Advisory
→
https://bugzilla.redhat.com/show_bug.cgi?id=2044156Issue Tracking · Third Party Advisory
→
https://gitlab.com/gnutls/gnutls/-/commit/3db352734472d851318944db13be73da61300568Patch · Third Party Advisory
→
https://gitlab.com/gnutls/gnutls/-/issues/1306Third Party Advisory
→
https://gitlab.com/gnutls/gnutls/-/merge_requests/1503Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20220915-0005/Third Party Advisory
Quick Facts
CVE IDCVE-2021-4209
CVSS Score6.5 / 10
SeverityMEDIUM
WeaknessCWE-476
CISA KEVNo
Affected3 vendor(s)
PublishedAug 24, 2022
Related CVEs (CWE-476)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-4209 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.