GnuTLS Stack Buffer Overflow in PKCS#11 Init Allows DoS/Code Exec
CVE-2025-9820 Published on January 26, 2026

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

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Vulnerability Analysis

CVE-2025-9820 is exploitable with local system access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a small impact on availability.

Attack Vector:
LOCAL
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
LOW

Timeline

Reported to Red Hat.

Made public. 77 days later.

Weakness Type

What is a Stack Overflow Vulnerability?

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).

CVE-2025-9820 has been classified to as a Stack Overflow vulnerability or weakness.


Products Associated with CVE-2025-9820

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2025-9820 are published in these products:

Red Hat Enterprise Linux (RHEL)
 
Red Hat Openshift
 
Canonical Ubuntu Linux
 
Red Hat Insights Proxy
 
Red Hat Rhui
 

Affected Versions

Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Insights proxy 1.5: Red Hat Update Infrastructure 5: Red Hat Update Infrastructure 5: Red Hat Update Infrastructure 5: Red Hat Update Infrastructure 5: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 7: Red Hat Enterprise Linux 8: Red Hat OpenShift Container Platform 4:

Exploit Probability

EPSS
0.01%
Percentile
1.03%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.