A flaw was found in gnutls. Servers configured with RSA-PSK (Rivest–Shamir–Adleman – Pre-Shared Key) wrongfully matched usernames containing a NUL character with truncated usernames. A remote attacker could exploit this by sending a specially crafted username, leading to an authentication bypass. This vulnerability allows an attacker to gain unauthorized access by circumventing the authentication process.
A flaw was found in gnutls. This vulnerability occurs because permitted name constraints were incorrectly ignored when previous Certificate Authorities (CAs) only had excluded name constraints. A remote attacker could exploit this to bypass critical name constraint checks during certificate validation. This bypass could lead to the acceptance of invalid certificates, potentially enabling spoofing or man-in-the-middle attacks against affected systems.
libgnutls: Servers configured with RSA-PSK have wrongfully matched usernames with NUL character in them to ones truncated to NUL character, which could lead to an authentication bypass. Fix the check to perform comparison up to the full username length. Reported by Joshua Rogers of AISLE Research Team. [GNUTLS-SA-2026-04-29-4, CVSS: high] [CVE-2026-42010]
libgnutls: Fix intersecting empty constraints Permitted name constraints were wrongfully ignored when prior CAs only had excluded name constraints, resulting in a name constraint bypass. Reported by .
libgnutls: Suppress CN fallback for oversized SAN Validation of certificates with oversized Subject Alternative Names no longer falls back to checking DNS hostnames against Common Name.
libgnutls: Fix off-by-one in PKCS#12 bag element bounds check Appending to a PKCS#12 bag that already contained 32 elements could write past the bag's internal array. Reported by Zou Dikai.
libgnutls: Fix overread in RSA key exchange with PKCS#11 keys For a server using an RSA key backed by a PKCS#11 token, a client sending an extremely short premaster secret during an RSA key exchange could trigger a short heap overread.
libgnutls: Suppress CN fallback in presence of URI and SRV SAN Certificates containing URI or SRV Subject Alternative Names no longer fall back to checking DNS hostnames against Common Name to avoid potential misuse of such certificates beyond their original purpose.
libgnutls: Fix use-after-free in gnutlspkcs11tokensetpin Changing the Security Officer PIN with gnutlspkcs11tokensetpin() with oldpin == NULL for a token lacking a protected authentication path led to a use-after-free.
libgnutls: Fix timing side-channel in PKCS#7 padding removal The PKCS#7 padding check performed during decryption was not constant-time, potentially leaking information about the padding bytes through timing differences. Rewritten to remove padding in a branch-free manner.