CVE-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.

Published: 2022-08-24 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-4209 is rated Moderate Risk (46.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.37%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-4209

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-07 0.34% 0.37% +0.02%
2 2026-02-21 0.21% 0.34% +0.14%
3 2026-01-18 — 0.21% —

Full EPSS history (15 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-4209

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]

Weakness enumeration for CVE-2021-4209

OS Trackers for CVE-2021-4209

vendor priority summary link
alpine medium CVE-2021-4209: 1 source package rows (gnutls); 30 state rows across 5 repos (3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 30. https://security.alpinelinux.org/vuln/CVE-2021-4209
debian not yet assigned CVE-2021-4209 not yet assigned priority: Debian including 1 source packages (gnutls28), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-4209
redhat low — https://access.redhat.com/security/cve/CVE-2021-4209
suse medium CVE-2021-4209 severity moderate: SUSE including 304 source package names (0.21.0.1.8.1:libgnutls30-3.6.7-14.16.1, 0.21.0.1.8.1:libgnutls30-hmac-3.6.7-14.16.1, …), 511 product×package rows across 103 product lines (Container caasp/v4/cilium, Container caasp/v4/cilium-operator, … (103 product lines)): Fixed 306, Known Affected 181, Known Not Affected 24. https://www.suse.com/security/cve/CVE-2021-4209/
ubuntu low CVE-2021-4209 low priority: Ubuntu including 2 source packages (gnutls26, gnutls28), 33 status rows across 19 suites (bionic, cosmic, disco, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 17, not-affected 8, released 4, ignored 2, needs-triage 2. https://ubuntu.com/security/CVE-2021-4209

Affected software / configurations for CVE-2021-4209

Vendor Product Version Raw CPE
gnu gnutls < 3.7.3 cpe:2.3:a:gnu:gnutls:*:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
netapp active_iq_unified_manager — cpe:2.3:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:*
netapp solidfire_\&_hci_management_node — cpe:2.3:a:netapp:solidfire_\&_hci_management_node:-:*:*:*:*:*:*:*
netapp hci_bootstrap_os — cpe:2.3:a:netapp:hci_bootstrap_os:-:*:*:*:*:*:*:*

References for CVE-2021-4209

cvelogic Threat Intelligence