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MEDIUM

CVE-2025-9820

CVSS v3

4

MEDIUM

EPSS Score

0.2 %

exploit probability, as of 2026-10-15

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • gnutlsAlmaLinux:10all versions · fixed in 3.8.10-3.el10_1and 5 other packages
  • gnutlsAlmaLinux:9all versions · fixed in 3.8.3-10.el9_7and 4 other packages
  • gnutlsAlmaLinux:8all versions · fixed in 3.6.16-8.el8_10.5and 4 other packages

Vendor advisories

  • CVE-2025-9820 Red Hat Product Security270 products fixed · 13 known affected

    gnutls: Stack-based Buffer Overflow in gnutls_pkcs11_token_init() Function

    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

  • ICSA-26-134-10 CISA1 known affected

    Siemens SIMATIC

    SIMATIC CN 4100

  • SSA-032379 Siemens ProductCERT1 known affected

    SSA-032379: Multiple Vulnerabilities in SIMATIC CN 4100 Before V5.0

    SIMATIC CN 4100

  • RHSA-2026:13812 Red Hat Product Security7 products fixed

    Red Hat Security Advisory: updated RHEL-8 based Middleware Containers container images

  • RHSA-2026:7477 Red Hat Product Security17 products fixed

    Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

  • RHSA-2026:7329 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: A Subscription Management tool for finding and reporting Red Hat product usage

6 more advisories

Full record on NVD

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.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Published
2026-01-26
Last Modified
2026-05-05

Frequently asked questions

What is CVE-2025-9820?

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.

Is CVE-2025-9820 actively exploited?

Active exploitation of CVE-2025-9820 has not been confirmed. Its EPSS score was 0.2% on 2026-10-15, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2025-9820?

CVE-2025-9820 has a CVSS v3 base score of 4 (MEDIUM severity), with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

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