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.

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.

GnuTLS is a secure communications library implementing the SSL, TLS and DTLS protocols and technologies around them. It provides a simple C language application programming interface (API) to access the secure communications protocols as well as APIs to parse and write X.509, PKCS #12, and other required structures. The project strives to provide a secure communications back-end, simple to use and integrated with the rest of the base Linux libraries. A back-end designed to work and be secure out of the box, keeping the complexity of TLS and PKI out of application code.

Security Fix(es):

(CVE-2025-9820)

GnuTLS is a secure communications library implementing the SSL, TLS and DTLS protocols and technologies around them. It provides a simple C language application programming interface (API) to access the secure communications protocols as well as APIs to parse and write X.509, PKCS #12, and other required structures. The project strives to provide a secure communications back-end, simple to use and integrated with the rest of the base Linux libraries. A back-end designed to work and be secure out of the box, keeping the complexity of TLS and PKI out of application code.

Security Fix(es):

(CVE-2025-9820)

GnuTLS is a secure communications library implementing the SSL, TLS and DTLS protocols and technologies around them. It provides a simple C language application programming interface (API) to access the secure communications protocols as well as APIs to parse and write X.509, PKCS #12, and other required structures. The project strives to provide a secure communications back-end, simple to use and integrated with the rest of the base Linux libraries. A back-end designed to work and be secure out of the box, keeping the complexity of TLS and PKI out of application code.

Security Fix(es):

(CVE-2025-9820)

GnuTLS is a secure communications library implementing the SSL, TLS and DTLS protocols and technologies around them. It provides a simple C language application programming interface (API) to access the secure communications protocols as well as APIs to parse and write X.509, PKCS #12, and other required structures. The project strives to provide a secure communications back-end, simple to use and integrated with the rest of the base Linux libraries. A back-end designed to work and be secure out of the box, keeping the complexity of TLS and PKI out of application code.

Security Fix(es):

(CVE-2025-9820)

GnuTLS is a secure communications library implementing the SSL, TLS and DTLS protocols and technologies around them. It provides a simple C language application programming interface (API) to access the secure communications protocols as well as APIs to parse and write X.509, PKCS #12, and other required structures. The project strives to provide a secure communications back-end, simple to use and integrated with the rest of the base Linux libraries. A back-end designed to work and be secure out of the box, keeping the complexity of TLS and PKI out of application code.

Security Fix(es):

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.(CVE-2025-9820)

The gnutls packages provide the GNU Transport Layer Security (GnuTLS) library, which implements cryptographic algorithms and protocols such as SSL, TLS, and DTLS.

Security Fix(es):

• gnutls: Stack-based Buffer Overflow in gnutls_pkcs11_token_init() Function (CVE-2025-9820)

• gnutls: GnuTLS: Denial of Service via excessive resource consumption during certificate verification (CVE-2025-14831)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The gnutls packages provide the GNU Transport Layer Security (GnuTLS) library, which implements cryptographic algorithms and protocols such as SSL, TLS, and DTLS.

Security Fix(es):

• gnutls: Stack-based Buffer Overflow in gnutls_pkcs11_token_init() Function (CVE-2025-9820)

• gnutls: GnuTLS: Denial of Service via excessive resource consumption during certificate verification (CVE-2025-14831)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The gnutls packages provide the GNU Transport Layer Security (GnuTLS) library, which implements cryptographic algorithms and protocols such as SSL, TLS, and DTLS.

Security Fix(es):

• gnutls: Stack-based Buffer Overflow in gnutls_pkcs11_token_init() Function (CVE-2025-9820)

• gnutls: GnuTLS: Denial of Service via excessive resource consumption during certificate verification (CVE-2025-14831)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Root has patched CVE-2025-9820 in the rootio-gnutls package for Root:Alpine:3.22. Multiple fixed versions available.

Root has patched CVE-2025-9820 in the rootio-gnutls28 package for Root:Debian:12. Multiple fixed versions available.

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.

The gnutls packages provide the GNU Transport Layer Security (GnuTLS) library, which implements cryptographic algorithms and protocols such as SSL, TLS, and DTLS.

Security Fix(es):

• gnutls: Stack-based Buffer Overflow in gnutls_pkcs11_token_init() Function (CVE-2025-9820)
• gnutls: GnuTLS: Denial of Service via excessive resource consumption during certificate verification (CVE-2025-14831)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The gnutls packages provide the GNU Transport Layer Security (GnuTLS) library, which implements cryptographic algorithms and protocols such as SSL, TLS, and DTLS.

Security Fix(es):

• gnutls: Stack-based Buffer Overflow in gnutls_pkcs11_token_init() Function (CVE-2025-9820)
• gnutls: GnuTLS: Denial of Service via excessive resource consumption during certificate verification (CVE-2025-14831)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The gnutls packages provide the GNU Transport Layer Security (GnuTLS) library, which implements cryptographic algorithms and protocols such as SSL, TLS, and DTLS.

Security Fix(es):

• gnutls: Stack-based Buffer Overflow in gnutls_pkcs11_token_init() Function (CVE-2025-9820)
• gnutls: GnuTLS: Denial of Service via excessive resource consumption during certificate verification (CVE-2025-14831)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

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.

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.

• CVE-2025-9820: fix stack-based buffer overflow in gnutls_pkcs11_token_init when processing overly long PKCS#11 token labels

• CVE-2025-6395: harden TLS 1.3 handshake state handling around PSK binders
• CVE-2025-9820: harden PKCS#11 token initialization against malformed input

Stack write buffer overflow. (CVE-2025-9820)

These are all security issues fixed in the gnutls-3.8.11-1.1 package on the GA media of openSUSE Tumbleweed.

This update for gnutls fixes the following issues:

• CVE-2025-14831: Fixed DoS via excessive resource consumption during certificate verification. (bsc#1257960)
• CVE-2025-9820: Fixed a buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)
• Add the functionality to allow to specify the hash algorithm for the PSK. This fixes a bug in the current implementation where the binder is always calculated with SHA256. (bsc#1258083, jsc#PED-15752, jsc#PED-15753)

This update for gnutls fixes the following issues:

• CVE-2025-9820: Fixed buffer overflow in gnutls_pkcs11_token_init (bsc#1254132).

This update for gnutls fixes the following issues:

• CVE-2025-9820: Fixed buffer overflow in gnutls_pkcs11_token_init (bsc#1254132).

This update for gnutls fixes the following issues:

• CVE-2025-9820: Fixed buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)

This update for gnutls fixes the following issues:

• CVE-2025-9820: Fixed buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)

This update for gnutls fixes the following issues:

• CVE-2025-9820: Fixed buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)

This update for gnutls fixes the following issues:

• CVE-2025-9820: Fixed buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)

This update for gnutls fixes the following issues:

• CVE-2025-9820: Fixed buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)

This update for gnutls fixes the following issues:

• CVE-2025-14831: Fixed DoS via excessive resource consumption during certificate verification. (bsc#1257960)
• CVE-2025-9820: Fixed a buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)
• Add the functionality to allow to specify the hash algorithm for the PSK. This fixes a bug in the current implementation where the binder is always calculated with SHA256. (bsc#1258083, jsc#PED-15752, jsc#PED-15753)

This update for gnutls fixes the following issues:

• CVE-2025-14831: Fixed DoS via excessive resource consumption during certificate verification. (bsc#1257960)
• CVE-2025-9820: Fixed a buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)
• Add the functionality to allow to specify the hash algorithm for the PSK. This fixes a bug in the current implementation where the binder is always calculated with SHA256. (bsc#1258083, jsc#PED-15752, jsc#PED-15753)

This update for gnutls fixes the following issues:

• CVE-2025-14831: Fixed DoS via excessive resource consumption during certificate verification. (bsc#1257960)
• CVE-2025-9820: Fixed a buffer overflow in gnutls_pkcs11_token_init. (bsc#1254132)
• Add the functionality to allow to specify the hash algorithm for the PSK. This fixes a bug in the current implementation where the binder is always calculated with SHA256. (bsc#1258083, jsc#PED-15752, jsc#PED-15753)

This update for gnutls fixes the following issues

• CVE-2026-33845: buffers: switch from end_offset over to frag_length (bsc#1263704).
• CVE-2026-33846: buffers: add more checks to DTLS reassembly (bsc#1263705).
• CVE-2026-42009: lib/buffers: ensure packets have differing sequence numbers (bsc#1263708).

Tim Scheckenbach discovered that GnuTLS incorrectly handled malicious certificates containing a large number of name constraints and subject alternative names. A remote attacker could possibly use this issue to cause GnuTLS to consume resources, resulting in a denial of service. (CVE-2025-14831)

Luigino Camastra discovered that GnuTLS incorrectly handled certain PKCS11 token labels. A remote attacker could use this issue to cause GnuTLS to crash, resulting in a denial of service, or possibly execute arbitrary code. The default compiler options for affected releases should reduce the vulnerability to a denial of service. (CVE-2025-9820)

It was discovered that GnuTLS had a timing side-channel when processing malformed ciphertexts in RSA-PSK ClientKeyExchange. A remote attacker could possibly use this issue to recover sensitive information. This issue only affected Ubuntu 18.04 LTS. (CVE-2024-0553)

Bing Shi discovered that GnuTLS incorrectly handled decoding certain DER-encoded certificates. A remote attacker could possibly use this issue to cause GnuTLS to consume resources, leading to a denial of service. This issue only affected Ubuntu 18.04 LTS. (CVE-2024-12243)

Luigino Camastra discovered that GnuTLS incorrectly handled certain PKCS11 token labels. A remote attacker could use this issue to cause GnuTLS to crash, resulting in a denial of service, or possibly execute arbitrary code. The default compiler options for affected releases should reduce the vulnerability to a denial of service. (CVE-2025-9820)

Tim Scheckenbach discovered that GnuTLS incorrectly handled malicious certificates containing a large number of name constraints and subject alternative names. A remote attacker could possibly use this issue to cause GnuTLS to consume resources, resulting in a denial of service. This issue only affected Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2025-14831)

Oleh Konko and Joshua Rogers discovered that GnuTLS did not properly handle case-insensitive name constraints in certain cases. A remote attacker could possibly use this issue to bypass certificate validation, leading to a machine-in-the-middle attack. (CVE-2026-3833)

Joshua Rogers discovered that GnuTLS did not properly handle very short premaster secrets in certain RSA key exchange cases with PKCS#11-backed server keys. A remote attacker could possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2026-5260)

Joshua Rogers discovered that GnuTLS did not properly handle malformed DTLS handshake fragments in certain cases. A remote attacker could possibly use this issue to obtain sensitive information, or cause a denial of service. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-33845)

Haruto Kimura, Oscar Reparaz, and Zou Dikai discovered that GnuTLS did not properly validate DTLS handshake fragment lengths in certain cases. A remote attacker could possibly use this issue to cause GnuTLS to crash, resulting in a denial of service, or execute arbitrary code. (CVE-2026-33846)

Joshua Rogers discovered that GnuTLS did not properly order DTLS packets with duplicate sequence numbers in certain cases. A remote attacker could possibly use this issue to cause GnuTLS to crash, resulting in a denial of service. (CVE-2026-42009)

Joshua Rogers discovered that GnuTLS did not properly handle usernames containing NUL characters in certain RSA-PSK configurations. A remote attacker could possibly use this issue to bypass authentication and gain unintended access to services. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-42010)