NVD / CVE Program· CNA redhat

CVE-2021-4209: A NULL pointer dereference flaw was found in GnuTLS.

Noroxi assessment

Priority: Monitor (action score 27/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 1.9% (FIRST EPSS); higher than 79.7% of all records.
Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: gnutls28 (Debian:10) 3.6.7-4+deb10u9; gnutls28 (Debian:12) 3.7.3-2; gnutls (openSUSE:Leap 15.3) 3.6.7-14.16.1.

Low priority for now. Upgrade to gnutls28 (Debian:10) 3.6.7-4+deb10u9; gnutls28 (Debian:12) 3.7.3-2; gnutls (openSUSE:Leap 15.3) 3.6.7-14.16.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 6.5 · v3.1—No exploit Fix available

Published: Aug 24, 2022
Updated: Oct 14, 2026
EPSS: 1.9% · 79th percentile
CWE: CWE-476

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 26 / 40 · 6.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 1.9%

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
gnu	gnutls	cpe:2.3:a:gnu:gnutls
redhat	enterprise linux	cpe:2.3:o:redhat:enterprise_linux
netapp	active iq unified manager	cpe:2.3:a:netapp:active_iq_unified_manager
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
netapp	hci compute node	cpe:2.3:h:netapp:hci_compute_node

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The GnuTLS version can't be seen from outside; the free SSL checker tests your certificate, enabled TLS versions and weak ciphers. Confirm the version on your server with the package manager.

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

gnu gnutlsbefore 3.7.3
netapp active iq unified managerall versions
netapp hci bootstrap osall versions
netapp solidfire & hci management nodeall versions
redhat enterprise linux8.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

n/a GnuTLS
- Fixed in gnutls v3.7.3affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:10	gnutls28	before 3.6.7-4+deb10u9	3.6.7-4+deb10u9
Debian:12	gnutls28	before 3.7.3-2	3.7.3-2
openSUSE:Leap 15.3	gnutls	before 3.6.7-14.16.1	3.6.7-14.16.1
SUSE:Linux Enterprise High Performance Computing 15-ESPOS	gnutls	before 3.6.7-150000.6.45.2	3.6.7-150000.6.45.2
SUSE:Linux Enterprise Module for Basesystem 15 SP3	gnutls	before 3.6.7-14.16.1	3.6.7-14.16.1
SUSE:Linux Enterprise Server 12 SP5	gnutls	before 3.4.17-8.11.1	3.4.17-8.11.1
SUSE:Linux Enterprise Software Development Kit 12 SP5	gnutls	before 3.3.27-3.6.1	3.3.27-3.6.1

Same product

gnu: all records

Other highest-scoring records for the same primary product.

CVE-2017-5334Double free vulnerability in the gnutls_x509_ext_import_proxy function in GnuTLS before 3.3.26 and 3.5.x before 3.5.8 allows remote attacker
49Plan
CVE-2019-3829A vulnerability was found in gnutls versions from 3.5.8 before 3.6.7.
48Plan
CVE-2008-1948The _gnutls_server_name_recv_params function in lib/ext_server_name.c in libgnutls in gnutls-serv in GnuTLS before 2.2.4 does not properly c
44Plan

Published before and after this one in the same product

← EarlierCVE-2021-20232Mar 12, 2021 · A flaw was found in gnutls.
40Plan
← EarlierCVE-2022-2509Aug 1, 2022 · A vulnerability found in gnutls.
31Monitor
Later →CVE-2023-0361Feb 15, 2023 · A timing side-channel in the handling of RSA ClientKeyExchange messages was discovered in GnuTLS.
29Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
debian:gnutls28	3.7.3-2 · Debian:12	Package registry (OSV)
opensuse:gnutls	3.6.7-14.16.1 · openSUSE:Leap 15.3	Package registry (OSV)
suse:gnutls	3.3.27-3.6.1 · SUSE:Linux Enterprise Software Development Kit 12 SP5	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-476 · NULL Pointer Dereference

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:46 PM UTC

For records you follow, these changes also arrive as notifications. →

References

access.redhat.com/security/cve/CVE-2021-4209

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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