CVE-2026-42010

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. 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.

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 heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The issue arises in merge_handshake_packet() where incoming handshake fragments are matched and merged based solely on handshake type, without validating that the message_length field remains consistent across all fragments of the same logical message. An attacker can exploit this by sending crafted DTLS fragments with conflicting message_length values, causing the implementation to allocate a buffer based on a smaller initial fragment and subsequently write beyond its bounds using larger, inconsistent fragments. Because the merge operation does not enforce proper bounds checking against the allocated buffer size, this results in an out-of-bounds write on the heap. The vulnerability is remotely exploitable without authentication via the DTLS handshake path and can lead to application crashes or potential memory corruption.(CVE-2026-33846)

A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of nameConstraints labels, specifically for dNSName (DNS) or rfc822Name (email) constraints within excludedSubtrees or permittedSubtrees. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.(CVE-2026-3833)

(CVE-2026-42009)

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.(CVE-2026-42010)

(CVE-2026-42013)

(CVE-2026-42014)

(CVE-2026-42015)

(CVE-2026-5260)

(CVE-2026-5419)

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 heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The issue arises in merge_handshake_packet() where incoming handshake fragments are matched and merged based solely on handshake type, without validating that the message_length field remains consistent across all fragments of the same logical message. An attacker can exploit this by sending crafted DTLS fragments with conflicting message_length values, causing the implementation to allocate a buffer based on a smaller initial fragment and subsequently write beyond its bounds using larger, inconsistent fragments. Because the merge operation does not enforce proper bounds checking against the allocated buffer size, this results in an out-of-bounds write on the heap. The vulnerability is remotely exploitable without authentication via the DTLS handshake path and can lead to application crashes or potential memory corruption.(CVE-2026-33846)

A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of nameConstraints labels, specifically for dNSName (DNS) or rfc822Name (email) constraints within excludedSubtrees or permittedSubtrees. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.(CVE-2026-3833)

(CVE-2026-42009)

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.(CVE-2026-42010)

(CVE-2026-42013)

(CVE-2026-42014)

(CVE-2026-42015)

(CVE-2026-5260)

(CVE-2026-5419)

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 heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The issue arises in merge_handshake_packet() where incoming handshake fragments are matched and merged based solely on handshake type, without validating that the message_length field remains consistent across all fragments of the same logical message. An attacker can exploit this by sending crafted DTLS fragments with conflicting message_length values, causing the implementation to allocate a buffer based on a smaller initial fragment and subsequently write beyond its bounds using larger, inconsistent fragments. Because the merge operation does not enforce proper bounds checking against the allocated buffer size, this results in an out-of-bounds write on the heap. The vulnerability is remotely exploitable without authentication via the DTLS handshake path and can lead to application crashes or potential memory corruption.(CVE-2026-33846)

A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of nameConstraints labels, specifically for dNSName (DNS) or rfc822Name (email) constraints within excludedSubtrees or permittedSubtrees. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.(CVE-2026-3833)

(CVE-2026-42009)

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.(CVE-2026-42010)

(CVE-2026-42013)

(CVE-2026-42014)

(CVE-2026-42015)

(CVE-2026-5260)

(CVE-2026-5419)

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 gnutls. A remote attacker could exploit an issue in the Datagram Transport Layer Security (DTLS) packet reordering logic. The comparator function, responsible for ordering DTLS packets by sequence numbers, did not correctly handle packets with duplicate sequence numbers. This could lead to unstable packet ordering or undefined behavior, resulting in a denial of service.(CVE-2026-42009)

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.(CVE-2026-42010)

(CVE-2026-42013)

(CVE-2026-42014)

(CVE-2026-42015)

(CVE-2026-5260)

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 gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of nameConstraints labels, specifically for dNSName (DNS) or rfc822Name (email) constraints within excludedSubtrees or permittedSubtrees. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.(CVE-2026-3833)

A flaw was found in gnutls. A remote attacker could exploit an issue in the Datagram Transport Layer Security (DTLS) packet reordering logic. The comparator function, responsible for ordering DTLS packets by sequence numbers, did not correctly handle packets with duplicate sequence numbers. This could lead to unstable packet ordering or undefined behavior, resulting in a denial of service.(CVE-2026-42009)

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.(CVE-2026-42010)

(CVE-2026-42013)

(CVE-2026-42014)

(CVE-2026-42015)

(CVE-2026-5260)

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

Security Fix(es):

• gnutls: Add more checks to DTLS reassembly (CVE-2026-33846)
• gnutls: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)
• gnutls: Fix crashing on an underflow with a DTLS datagram (CVE-2026-33845)
• gnutls: Fix RSA-PSK identity truncation (CVE-2026-42010)
• gnutls: Fix case-sensitivity of domain name comparison in name constraints (CVE-2026-3833)
• gnutls: Fix intersecting empty constraints (CVE-2026-42011)

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: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)
• gnutls: Fix crashing on an underflow with a DTLS datagram (CVE-2026-33845)
• gnutls: Fix RSA-PSK identity truncation (CVE-2026-42010)
• gnutls: Fix case-sensitivity of domain name comparison in name constraints (CVE-2026-3833)
• gnutls: Fix intersecting empty name constraints (CVE-2026-42011)
• gnutls: Denial of Service via heap buffer overflow in DTLS handshake fragment reassembly (CVE-2026-33846)

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: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)
• gnutls: Fix crashing on an underflow with a DTLS datagram (CVE-2026-33845)
• gnutls: Fix RSA-PSK identity truncation (CVE-2026-42010)
• gnutls: Fix case-sensitivity of domain name comparison in name constraints (CVE-2026-3833)
• gnutls: Fix intersecting empty name constraints (CVE-2026-42011)
• gnutls: Denial of Service via heap buffer overflow in DTLS handshake fragment reassembly (CVE-2026-33846)

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-2026-42010 in the rootio-gnutls28 package for Root:Debian:12. Multiple fixed versions available.

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.

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

Security Fix(es):

• gnutls: Add more checks to DTLS reassembly (CVE-2026-33846)
• gnutls: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)
• gnutls: Fix crashing on an underflow with a DTLS datagram (CVE-2026-33845)
• gnutls: Fix RSA-PSK identity truncation (CVE-2026-42010)
• gnutls: Fix case-sensitivity of domain name comparison in name constraints (CVE-2026-3833)
• gnutls: Fix intersecting empty constraints (CVE-2026-42011)

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: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)
• gnutls: Fix crashing on an underflow with a DTLS datagram

(CVE-2026-33845)

• gnutls: Fix RSA-PSK identity truncation (CVE-2026-42010)
• gnutls: Fix case-sensitivity of domain name comparison in name

constraints (CVE-2026-3833)

• gnutls: Fix intersecting empty name constraints (CVE-2026-42011)
• gnutls: Denial of Service via heap buffer overflow in DTLS handshake

fragment reassembly (CVE-2026-33846)

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: Fix qsort comparator in DTLS reassembly (CVE-2026-42009)
• gnutls: Fix crashing on an underflow with a DTLS datagram (CVE-2026-33845)
• gnutls: Fix RSA-PSK identity truncation (CVE-2026-42010)
• gnutls: Fix case-sensitivity of domain name comparison in name constraints (CVE-2026-3833)
• gnutls: Fix intersecting empty name constraints (CVE-2026-42011)
• gnutls: Denial of Service via heap buffer overflow in DTLS handshake fragment reassembly (CVE-2026-33846)

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 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.

• SECURITY UPDATE: Authentication bypass via NUL-byte truncation in RSA-PSK username lookup
  • debian/patches/CVE-2026-42010.patch: replace strlen(info->username) with info->username_len in _gnutls_proc_rsa_psk_client_kx in lib/auth/rsa_psk.c to prevent NUL-byte truncation allowing username matching with truncated entries
  • CVE-2026-42010

• CVE-2026-42010: server-side RSA-PSK authentication bypass via NUL-byte truncation of binary PSK identities in _gnutls_proc_rsa_psk_client_kx

• CVE-2026-42010: fix RSA-PSK identity truncation allowing authentication bypass via NUL byte in client-supplied username

• CVE-2026-42010: server RSA-PSK key exchange truncates the binary PSK identity at the first NUL byte when looking up the pre-shared key, causing usernames containing embedded NUL bytes to match shorter legitimate identities and allowing authentication bypass

• CVE-2026-42010: RSA-PSK server truncated PSK identity at an embedded NUL byte during _gnutls_psk_pwd_find_entry lookup, allowing authentication bypass; use info->username_len instead of strlen(info->username)

• CVE-2026-42010: RSA-PSK server truncated PSK identity at an embedded NUL byte during _gnutls_psk_pwd_find_entry lookup, allowing authentication bypass; use info->username_len instead of strlen(info->username)

These are all security issues fixed in the gnutls-3.8.13-1.1 package on the GA media of openSUSE Tumbleweed.

This update for gnutls fixes the following issues

• CVE-2026-3832: cert-session: fix multi-entry OCSP revocation bypass (bsc#1263706).
• CVE-2026-3833: x509/name-constraints: compare domain names case-insensitive (bsc#1263707).
• CVE-2026-5260: lib/pkcs11_privkey: guard against overreading on short ciphertexts (bsc#1263715).
• CVE-2026-5419: gnutls_cipher_decrypt3: make PKCS#7 unpadding branch free (bsc#1263716).
• 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).
• CVE-2026-42010: lib/auth/rsa_psk: fix binary PSK identity lookup (bsc#1263709).
• CVE-2026-42011: x509/name_constraints: fix intersecting empty constraints (bsc#1263710).
• CVE-2026-42012: x509/hostname-verify: make URI/SRV SAN preclude CN fallback (bsc#1263711).
• CVE-2026-42013: x509: prevent fallback on oversized SAN (bsc#1263712).
• CVE-2026-42014: pkcs11_write: fix UAF and leak in gnutls_pkcs11_token_set_pin (bsc#1263713).
• CVE-2026-42015: x509/pkcs12_bag: fix off-by-one in bag element bounds chec (bsc#1263714).

Root has patched CVE-2026-42010 in the rootio-gnutls28 package for Root:Debian:13. Multiple fixed versions available.

This update for gnutls fixes the following issues

• CVE-2026-3833: x509/name-constraints: compare domain names case-insensitive (bsc#1263707).
• CVE-2026-5260: lib/pkcs11_privkey: guard against overreading on short ciphertexts (bsc#1263715).
• 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).
• CVE-2026-42010: lib/auth/rsa_psk: fix binary PSK identity lookup (bsc#1263709).
• CVE-2026-42011: x509/name_constraints: fix intersecting empty constraints (bsc#1263710).
• CVE-2026-42012: x509/hostname-verify: make URI/SRV SAN preclude CN fallback (bsc#1263711).
• CVE-2026-42013: x509: prevent fallback on oversized SAN (bsc#1263712).
• CVE-2026-42014: pkcs11_write: fix UAF and leak in gnutls_pkcs11_token_set_pin (bsc#1263713).
• CVE-2026-42015: x509/pkcs12_bag: fix off-by-one in bag element bounds chec (bsc#1263714).

This update for gnutls fixes the following issues

• CVE-2026-3833: x509/name-constraints: compare domain names case-insensitive (bsc#1263707).
• CVE-2026-5260: lib/pkcs11_privkey: guard against overreading on short ciphertexts (bsc#1263715).
• CVE-2026-5419: gnutls_cipher_decrypt3: make PKCS#7 unpadding branch free (bsc#1263716).
• 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).
• CVE-2026-42010: lib/auth/rsa_psk: fix binary PSK identity lookup (bsc#1263709).
• CVE-2026-42011: x509/name_constraints: fix intersecting empty constraints (bsc#1263710).
• CVE-2026-42012: x509/hostname-verify: make URI/SRV SAN preclude CN fallback (bsc#1263711).
• CVE-2026-42013: x509: prevent fallback on oversized SAN (bsc#1263712).
• CVE-2026-42014: pkcs11_write: fix UAF and leak in gnutls_pkcs11_token_set_pin (bsc#1263713).
• CVE-2026-42015: x509/pkcs12_bag: fix off-by-one in bag element bounds chec (bsc#1263714).

This update for gnutls fixes the following issues

• CVE-2026-3832: cert-session: fix multi-entry OCSP revocation bypass (bsc#1263706).
• CVE-2026-3833: x509/name-constraints: compare domain names case-insensitive (bsc#1263707).
• CVE-2026-5260: lib/pkcs11_privkey: guard against overreading on short ciphertexts (bsc#1263715).
• CVE-2026-5419: gnutls_cipher_decrypt3: make PKCS#7 unpadding branch free (bsc#1263716).
• 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).
• CVE-2026-42010: lib/auth/rsa_psk: fix binary PSK identity lookup (bsc#1263709).
• CVE-2026-42011: x509/name_constraints: fix intersecting empty constraints (bsc#1263710).
• CVE-2026-42012: x509/hostname-verify: make URI/SRV SAN preclude CN fallback (bsc#1263711).
• CVE-2026-42013: x509: prevent fallback on oversized SAN (bsc#1263712).
• CVE-2026-42014: pkcs11_write: fix UAF and leak in gnutls_pkcs11_token_set_pin (bsc#1263713).
• CVE-2026-42015: x509/pkcs12_bag: fix off-by-one in bag element bounds chec (bsc#1263714).

This update for gnutls fixes the following issues

• CVE-2026-3833: x509/name-constraints: compare domain names case-insensitive (bsc#1263707).
• CVE-2026-5260: lib/pkcs11_privkey: guard against overreading on short ciphertexts (bsc#1263715).
• CVE-2026-5419: gnutls_cipher_decrypt3: make PKCS#7 unpadding branch free (bsc#1263716).
• 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).
• CVE-2026-42010: lib/auth/rsa_psk: fix binary PSK identity lookup (bsc#1263709).
• CVE-2026-42011: x509/name_constraints: fix intersecting empty constraints (bsc#1263710).
• CVE-2026-42012: x509/hostname-verify: make URI/SRV SAN preclude CN fallback (bsc#1263711).
• CVE-2026-42013: x509: prevent fallback on oversized SAN (bsc#1263712).
• CVE-2026-42014: pkcs11_write: fix UAF and leak in gnutls_pkcs11_token_set_pin (bsc#1263713).
• CVE-2026-42015: x509/pkcs12_bag: fix off-by-one in bag element bounds chec (bsc#1263714).

This update for gnutls fixes the following issues

• CVE-2026-3832: cert-session: fix multi-entry OCSP revocation bypass (bsc#1263706).
• CVE-2026-3833: x509/name-constraints: compare domain names case-insensitive (bsc#1263707).
• CVE-2026-5260: lib/pkcs11_privkey: guard against overreading on short ciphertexts (bsc#1263715).
• CVE-2026-5419: gnutls_cipher_decrypt3: make PKCS#7 unpadding branch free (bsc#1263716).
• 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).
• CVE-2026-42010: lib/auth/rsa_psk: fix binary PSK identity lookup (bsc#1263709).
• CVE-2026-42011: x509/name_constraints: fix intersecting empty constraints (bsc#1263710).
• CVE-2026-42012: x509/hostname-verify: make URI/SRV SAN preclude CN fallback (bsc#1263711).
• CVE-2026-42013: x509: prevent fallback on oversized SAN (bsc#1263712).
• CVE-2026-42014: pkcs11_write: fix UAF and leak in gnutls_pkcs11_token_set_pin (bsc#1263713).
• CVE-2026-42015: x509/pkcs12_bag: fix off-by-one in bag element bounds chec (bsc#1263714).

This update for gnutls fixes the following issues

• CVE-2026-3833: x509/name-constraints: compare domain names case-insensitive (bsc#1263707).
• CVE-2026-5260: lib/pkcs11_privkey: guard against overreading on short ciphertexts (bsc#1263715).
• CVE-2026-5419: gnutls_cipher_decrypt3: make PKCS#7 unpadding branch free (bsc#1263716).
• 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).
• CVE-2026-42010: lib/auth/rsa_psk: fix binary PSK identity lookup (bsc#1263709).
• CVE-2026-42011: x509/name_constraints: fix intersecting empty constraints (bsc#1263710).
• CVE-2026-42012: x509/hostname-verify: make URI/SRV SAN preclude CN fallback (bsc#1263711).
• CVE-2026-42013: x509: prevent fallback on oversized SAN (bsc#1263712).
• CVE-2026-42014: pkcs11_write: fix UAF and leak in gnutls_pkcs11_token_set_pin (bsc#1263713).
• CVE-2026-42015: x509/pkcs12_bag: fix off-by-one in bag element bounds chec (bsc#1263714).

This update for gnutls fixes the following issues

• CVE-2025-14831: excessive resource consumption when verifying specially crafted malicious certificates containing a large number of name constraints and SANs (bsc#1257960).
• CVE-2026-3833: incorrectly accepted domain names due to comparison during name constraints processing being case-sensitive (bsc#1263707).
• CVE-2026-5260: heap overread when processing extremely short premaster secret as part of an RSA key exchange (bsc#1263715).
• CVE-2026-33845: integer overflow and heap overrun when parsing fragments with zero length and non-zero offset during DTLS handshake (bsc#1263704).
• CVE-2026-33846: heap overwrite during DTLS handshake fragment reassembly due to missing validations and checks (bsc#1263705).
• CVE-2026-42009: undefined behavior resulting in a DoS when handling DTLS packets with duplicate sequence numbers (bsc#1263708).
• CVE-2026-42010: authentication bypass when processing a PSK username with a NUL-character (bsc#1263709).
• CVE-2026-42011: name constraint bypass leading to acceptance of invalid certificates during certificate validation (bsc#1263710).
• CVE-2026-42012: spoofing of legitimate services and sensitive information interception via specially crafted certificates containing URIs or SRV SANs. (bsc#1263711).
• CVE-2026-42013: certificate validation bypass when validating certificates with an oversized SAN (bsc#1263712).
• CVE-2026-42014: use-after-free when an attacker attempts to change the PIN with a NULL old PIN for a token that lacks a protected authentication path (bsc#1263713).
• CVE-2026-42015: memory corruption when appending to a PKCS#12 bag that already contains 32 elements (bsc#1263714).

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)