CVE-2025-9820: GnuTLS stack overflow in gnutls_pkcs11_token_init

CVE-2025-9820 · Severity: medium · CVSS 4 · Published 2026-01-26

GnuTLS is a widely used security library that enables encrypted communications for many Linux applications and services. A flaw in how it handles security tokens could allow a local attacker to crash applications or potentially gain higher privileges on the system. This could lead to service outages or unauthorized access to sensitive data on affected servers.

Technologies: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9. Vendors: Red Hat.

Quick answers

Is CVE-2025-9820 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-9820 being exploited in the wild.
How severe is CVE-2025-9820?
Medium severity, with a CVSS score of 4, published 26 January 2026.
Which products and versions are affected?
Red Hat Enterprise Linux 10 gnutls < 3.8.10-3.el10_1; Red Hat Enterprise Linux 8 gnutls < 3.6.16-8.el8_10.5; Red Hat Enterprise Linux 9 gnutls < 3.8.3-10.el9_7.
Is there a fix for CVE-2025-9820?
A patch was published on 2026-03-02: Red Hat released patches for RHEL 10 (RHSA-2026:3477) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2025-9820 attacked?
It is attacked with local access, in a software library.
Am I affected by CVE-2025-9820?
Check whether you run Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8 or Red Hat Enterprise Linux 9 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A stack-based buffer overflow (CWE-121) exists in the gnutls_pkcs11_token_init() function of the GnuTLS library. The vulnerability is triggered when the function processes a PKCS#11 token label that exceeds the size of a fixed-length stack buffer. An attacker with local access could provide a specially crafted token label to cause a denial of service (application crash) or potentially achieve arbitrary code execution for local privilege escalation. The issue has been addressed in various GnuTLS package updates across Red Hat Enterprise Linux versions 8, 9, and 10.

Affected products

  • GnuTLS GnuTLS versions prior to 3.8.10-3.el10_1, 3.6.16-8.el8_10.5, 3.8.3-10.el9_7
  • Red Hat Enterprise Linux 8 gnutls < 3.6.16-8.el8_10.5
  • Red Hat Enterprise Linux 9 gnutls < 3.8.3-10.el9_7
  • Red Hat Enterprise Linux 10 gnutls < 3.8.10-3.el10_1

Timeline

  • 2025-11-18: advisory: GnuTLS security advisory GNUTLS-SA-2025-11-18 released
  • 2026-01-26: disclosed: CVE published to NVD
  • 2026-03-02: patched: Red Hat released patches for RHEL 10 (RHSA-2026:3477)
  • 2026-05-05: patched: Red Hat released patches for Middleware Containers (RHSA-2026:13812)

References

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