USN-8284-1: GnuTLS vulnerabilities

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. (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)

Oleh Konko and Joshua Rogers discovered that GnuTLS did not properly
validate OCSP responses in certain cases. A remote attacker could
possibly use this issue to bypass certificate revocation checks, leading
to a machine-in-the-middle attack. (CVE-2026-3832)

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 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. (CVE-2026-42010)

Haruto Kimura discovered that GnuTLS did not properly apply permitted
name constraints in certain certificate validation paths. A remote
attacker could possibly use this issue to bypass certificate validation,
leading to a machine-in-the-middle attack. (CVE-2026-42011)

Oleh Konko discovered that GnuTLS incorrectly fell back to Common Name
checks for certain URI and SRV subject alternative names. A remote
attacker could possibly use this issue to bypass certificate validation,
leading to a machine-in-the-middle attack. (CVE-2026-42012)

Haruto Kimura and Joshua Rogers discovered that GnuTLS incorrectly fell
back to Common Name checks when subject alternative names were oversized.
A remote attacker could possibly use this issue to bypass certificate
validation, leading to a machine-in-the-middle attack. (CVE-2026-42013)

Luigino Camastra and Joshua Rogers discovered that GnuTLS had a
use-after-free issue when changing PKCS#11 token security officer PINs in
certain cases. An attacker could possibly use this issue to cause GnuTLS
to crash, resulting in a denial of service, or execute arbitrary code.
(CVE-2026-42014)

Zou Dikai discovered that GnuTLS did not properly validate PKCS#12 bag
sizes in certain cases. An attacker could possibly use this issue to
cause GnuTLS to crash, resulting in a denial of service, or execute
arbitrary code. (CVE-2026-42015)

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. (CVE-2026-5260)

Doria Tang discovered that GnuTLS did not perform PKCS#7 padding checks
in constant time in certain cases. A remote attacker could possibly use
this issue to obtain sensitive information. This issue only affected
Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-5419)