Full vulnerability report · 2026

CVE-2025-9820High confidence

Gnutls: stack-based buffer overflow in gnutls_pkcs11_token_init() function

Unknown · Unknown

4.0MediumCVSS 3.1

Recommended action

Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available

Distribution package intelligence

Ubuntu vendor package status

Canonical’s release and source-package findings are shown separately from local repository availability.

1 package state

Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Ubuntu release	Source package	Vendor state	Fixed version	Evidence
Ubuntu 24.04 LTSnoble · standard archive	`gnutls28`	Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.	`3.8.3-1.1ubuntu3.5`	Canonical record ↗Source updated 11 Sept 2026

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

2 current

CVE-2025-9820 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitygnutls: Stack-based Buffer Overflow in gnutls_pkcs11_token_init() Function

13 known affected

The vendor explicitly identifies these products as affected by this CVE.

gnutls as a component of Red Hat Enterprise Linux 6
gnutls-devel as a component of Red Hat Enterprise Linux 6
gnutls-guile as a component of Red Hat Enterprise Linux 6
gnutls-utils as a component of Red Hat Enterprise Linux 6
gnutls.src as a component of Red Hat Enterprise Linux 6
gnutls as a component of Red Hat Enterprise Linux 7
gnutls-c++ as a component of Red Hat Enterprise Linux 7
gnutls-dane as a component of Red Hat Enterprise Linux 7
gnutls-devel as a component of Red Hat Enterprise Linux 7
gnutls-utils as a component of Red Hat Enterprise Linux 7
gnutls.src as a component of Red Hat Enterprise Linux 7
openshift/ose-rhel-coreos-8 as a component of Red Hat OpenShift Container Platform 4

Summary: A flaw was found in the GnuTLS library, specifically in the gnutls_pkcs11_token_init() function that handles PKCS#11 token initialization. When a token label longer than expected is processed, the function writes past the end of a fixed-size stack buffer. This programming error can cause the application using GnuTLS to crash or, in certain conditions, be exploited for code execution. As a result, systems or applications relying on GnuTLS may be vulnerable to a denial of service or local privilege escalation attacks.
Remediation: The RHEL-8 based Middleware Containers container images provided by this update can be downloaded from the Red Hat Container Registry at registry.access.redhat.com. Installation instructions for your platform are available at Red Hat Container Catalog (see References). Dockerfiles and scripts should be amended either to refer to this new image specifically, or to the latest image generally.

SSA-032379 · CSAF 2.0 · revision 1 · interimSiemens ProductCERTSSA-032379: Multiple Vulnerabilities in SIMATIC CN 4100 Before V5.0

1 known affected

The vendor explicitly identifies these products as affected by this CVE.

SIMATIC CN 4100

Summary: A flaw was found in the GnuTLS library, specifically in the gnutls_pkcs11_token_init() function that handles PKCS#11 token initialization. When a token label longer than expected is processed, the function writes past the end of a fixed-size stack buffer. This programming error can cause the application using GnuTLS to crash or, in certain conditions, be exploited for code execution. As a result, systems or applications relying on GnuTLS may be vulnerable to a denial of service or local privilege escalation attacks.
Remediation: Update to V5.0 or later version

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current

ENISA EUVD identifier

EUVD-2025-206344

No EUVD known-exploited evidence

A flaw was found in the GnuTLS library, specifically in the gnutls_pkcs11_token_init() function that handles PKCS#11 token initialization. When a token label longer than expected is processed, the function writes past the end of a fixed-size stack buffer. This programming error can cause the application using GnuTLS to crash or, in certain conditions, be exploited for code execution. As a result, systems or applications relying on GnuTLS may be vulnerable to a denial of service or local privilege escalation attacks.

EUVD state: Present in the current official mapping
Known exploitation: Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score: 4.0 · CVSS 3.1
Advisory evidence: No linked advisory details stored yet

Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available

What, why and how

What

Why

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

How

An attacker operating through local access may attempt exploitation without authentication or user interaction. If successful, the issue may gain additional privileges.

What

Why

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

How

An attacker operating through local access may attempt exploitation without authentication or user interaction. If successful, the issue may gain additional privileges.

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path: local access → Stack-based Buffer Overflow → gain additional privileges
Attack surface: Local
Privileges required: None: unauthenticated exploitation is possible
User interaction: None
Attack complexity: Low: no specialised conditions are recorded
Security boundary: Unchanged: impact remains within the vulnerable component's security authority
Weakness ? CWE means Common Weakness Enumeration: a standard category for the underlying weakness.: CWE-121 ↗
CWE-121: Stack-based Buffer Overflow. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
CVSS vector ? CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.ALowAvailability impact: A successful attack can cause a limited loss.
Post-exploitation / living off the land: Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.

UnauthenticatedPrivilege escalationDenial of serviceCWE-121

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2025-206344Official EUVD mapping

Official EUVD record ↗

BSI · German · WID-SEC-2026-2253IBM Security Verify Access: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in IBM Security Verify Access ausnutzen, um erweiterte Berechtigungen zu erlangen, beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren, sensible Informationen offenzulegen und andere, nicht näher bezeichnete Angriffe durchzuführen.

Gnutls: stack-based buffer overflow in gnutls_pkcs11_token_init() function

National CERT insights ?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

EUVD-2025-206344

What, why and how

Exploit reality and attack path

Official authority intelligence

Patch and workaround

Evidence and provenance

National CERT insights
?
CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.