Medium Memory corruption

CVE-2021-4209 — A NULL pointer dereference flaw was found in GnuTLS. As Nettle's hash update functions internally...

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 Aug 24, 2022 · Updated Oct 14, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: redhat

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 1.7% (30-day exploitation probability)+12
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

1.75%

ahead of 77% of scored CVEs · Oct 14, 2026

Affects

Gnu

Gnutls and 4 more

CVSS base

6.5

Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — gitlab.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Gnu Gnutls, Netapp Active Iq Unified Manager, Netapp Hci Bootstrap Os…).
Apply the fixed version or the patch documented under Remediation.
Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Gnu	Gnutls	< 3.7.3	Vulnerable	NIST National Vulnerability Database
Netapp	Active Iq Unified Manager	versions not specified by the source	Vulnerable	NIST National Vulnerability Database
Netapp	Hci Bootstrap Os	versions not specified by the source	Vulnerable	NIST National Vulnerability Database
Netapp	Solidfire & Hci Management Node	versions not specified by the source	Vulnerable	NIST National Vulnerability Database
Red Hat	Enterprise Linux	version 8.0	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
6.5	CVSS 3.1	Medium	2.8	3.6	nvd@nist.gov via NIST National Vulnerability Database
6.5	CVSS 3.1	Medium	—	—	GitHub, Inc. via GitHub Security Advisories

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-476 · NULL Pointer Dereference

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 1.75%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.

web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 14, 2026
Fix documented
Oct 14, 2026 · NIST National Vulnerability Database
Affected products added · gnu/gnutls, redhat/enterprise linux, netapp/active iq unified manager, netapp/solidfire & hci management node, netapp/hc
Oct 14, 2026 · NIST National Vulnerability Database
CVSS changed · 6.5
Oct 14, 2026 · NIST National Vulnerability Database
Source status changed · → Modified
Oct 14, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 14, 2026 · Alertas do Telegram
2022
CVE published
Aug 24, 2022 · redhat

Source activity

Repeated readings are counted rather than listed.

2× References added · Oct 14, 2026 – Oct 14, 2026
1× Official description updated · Oct 14, 2026 – Oct 14, 2026

References

9 on the record

gitlab.com/gnutls/gnutls/-/commit/3db352734472d851318944db13be73da61300568
Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
security.netapp.com/advisory/ntap-20220915-0005/
Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
github.com/advisories/GHSA-xj78-h3gx-cm6v
GitHub Security Advisories
gitlab.com/gnutls/gnutls/-/issues/1306
Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
cert-portal.siemens.com/productcert/html/ssa-398330.html
NIST National Vulnerability Database
bugzilla.redhat.com/show_bug.cgi
Issue Tracking, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
gitlab.com/gnutls/gnutls/-/merge_requests/1503
Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
access.redhat.com/security/cve/CVE-2021-4209
Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2021-4209
GitHub Security Advisories

Elsewhere on this site

Gnu
every CVE for this vendor

Memory corruption
same class

CWE-476
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-104046 Sssd: sssd: denial of service via incomplete identity provider authentication requests 8d
Medium CVE-2026-104045 Sssd: sssd: denial of service via race condition in autofs responder 8d
High CVE-2026-104048 Sssd: sssd: authorization bypass via cross-domain username collision in hbac evaluation 9d
Medium CVE-2026-104047 Sssd: sssd: information disclosure via query injection in entra id lookups 9d
High CVE-2026-102558 Libsoup: libsoup: heap buffer overflow during websocket receive-buffer growth 16d
High CVE-2026-102555 Libsoup: libsoup: heap buffer overflow via uninitialized length in data-uri base64 decoding 16d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CISA SSVC assessment.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-4209 is "A NULL pointer dereference flaw was found in GnuTLS. As Nettle's hash update functions internally...", rated Medium. It affects Gnutls (Gnu); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.5 describes technical severity. EPSS 1.75% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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