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)