Red Hat Security Advisory: gnutls and libtasn1 security update

Fixed packages 48

Vulnerabilities 13

• High 8.2
  CVE-2026-42013

  Gnutls: gnutls: certificate validation bypass due to oversized subject alternative name

  A flaw was found in gnutls. When validating certificates, an oversized Subject Alternative Name (SAN) could cause the validation process to incorrectly fall back to checking the Common Name (CN) field. This could allow a remote attacker to bypass proper certi…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  May 26, 2026
• High 8.2
  CVE-2026-5260

  Gnutls: gnutls: information disclosure via heap overread in rsa key exchange

  A flaw was found in libgnutls. A remote attacker, by sending an extremely short premaster secret during an RSA key exchange to a server using an RSA key backed by a PKCS#11 token, could trigger a short heap overread. This memory corruption vulnerability could…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 7 Linux Debian Ubuntu Azure Linux Alpine
  May 26, 2026
• High 7.5
  CVE-2026-33845

  Gnutls: gnutls: denial of service via dtls zero-length fragment

  A flaw in GnuTLS DTLS handshake parsing allows malformed fragments with zero length and non-zero offset, leading to an integer underflow during reassembly and resulting in an out-of-bounds read. This issue is remotely exploitable and may cause information dis…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  Apr 30, 2026
• High 7.5
  CVE-2026-33846

  Gnutls: gnutls: denial of service via heap buffer overflow in dtls handshake fragment reassembly

  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 th…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  May 4, 2026
• High 7.5
  CVE-2026-42009

  Gnutls: gnutls: denial of service via dtls packet reordering vulnerability

  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 …

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  May 18, 2026
• High 7.4
  CVE-2026-42011

  Gnutls: gnutls: security bypass due to incorrect name constraint handling

  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 cons…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Alpine
  May 7, 2026
• High 7.1
  CVE-2026-42010

  Gnutls: gnutls: authentication bypass via nul character in username

  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…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 7 Linux Debian Ubuntu Azure Linux Alpine
  May 7, 2026
• High 7.1
  CVE-2026-42012

  Gnutls: gnutls: certificate validation bypass due to improper handling of uri and srv sans

  A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially crafted certificate that contains Uniform Resource Identifier (URI) or Service (SRV) Subject Alternative Names (SANs). This could cause the certificate va…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 10 Linux Debian Ubuntu Azure Linux Alpine
  May 26, 2026
• Medium 6.6
  CVE-2026-42014

  Gnutls: gnutls: use-after-free in gnutls_pkcs11_token_set_pin

  A flaw was found in GnuTLS. The `gnutls_pkcs11_token_set_pin` function, used for changing the Security Officer PIN, can lead to a use-after-free vulnerability. This occurs when an attacker attempts to change the PIN with a NULL old PIN for a token that lacks …

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  Jun 16, 2026
• Medium 6.5
  CVE-2026-3833

  Gnutls: gnutls: policy bypass due to case-sensitive nameconstraints comparison

  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 remo…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Alpine
  Apr 30, 2026
• Medium 5.3
  CVE-2024-12133

  Libtasn1: inefficient der decoding in libtasn1 leading to potential remote dos

  A flaw in libtasn1 causes inefficient handling of specific certificate data. When processing a large number of elements in a certificate, libtasn1 takes much longer than expected, which can slow down or even crash the system. This flaw allows an attacker to s…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 7 Linux Debian Ubuntu Azure Linux Alpine
  Feb 10, 2025
• Medium 5.3
  CVE-2025-14831

  Gnutls: gnutls: denial of service via excessive resource consumption during certificate verification

  A flaw was found in GnuTLS. This vulnerability allows a denial of service (DoS) by excessive CPU (Central Processing Unit) and memory consumption via specially crafted malicious certificates containing a large number of name constraints and subject alternativ…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 7 Linux Debian Ubuntu Alpine
  Feb 9, 2026
• Medium 5.3
  CVE-2026-42015

  Gnutls: gnutls: memory corruption due to off-by-one error in pkcs#12 bag handling

  A flaw was found in gnutls. An off-by-one error exists in the PKCS#12 bag element bounds check. This vulnerability allows an remote attacker to write past the internal array of a PKCS#12 bag when appending to a bag that already contains 32 elements. This memo…

  Red Hat Red Hat Enterprise Linux 9 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 6 Linux Debian Ubuntu Azure Linux Alpine
  May 26, 2026

References

• article
  https://access.redhat.com/security/updates/classification/#important
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2344611
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2423177
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2445763
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2450624
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2450625
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467279
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467289
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467437
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467441
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467448
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467450
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467451
• report
  https://bugzilla.redhat.com/show_bug.cgi?id=2467678
• advisory
  https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_30849.json
• report
  https://access.redhat.com/security/cve/CVE-2024-12133
• advisory
  https://www.cve.org/CVERecord?id=CVE-2024-12133
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2024-12133
• article
  https://gitlab.com/gnutls/libtasn1/-/blob/master/doc/security/CVE-2024-12133.md
• article
  https://gitlab.com/gnutls/libtasn1/-/issues/52
• report
  https://access.redhat.com/security/cve/CVE-2025-14831
• advisory
  https://www.cve.org/CVERecord?id=CVE-2025-14831
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2025-14831
• article
  https://gitlab.com/gnutls/gnutls/-/issues/1773
• report
  https://access.redhat.com/security/cve/CVE-2026-3833
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-3833
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-3833
• article
  https://gitlab.com/gnutls/gnutls/-/issues/1803
• report
  https://access.redhat.com/security/cve/CVE-2026-5260
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-5260
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-5260
• article
  https://www.gnutls.org/security-new.html#GNUTLS-SA-2026-04-29-10
• report
  https://access.redhat.com/security/cve/CVE-2026-33845
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-33845
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-33845
• report
  https://access.redhat.com/security/cve/CVE-2026-33846
• advisory
  https://www.cve.org/CVERecord?id=CVE-2026-33846
• advisory
  https://nvd.nist.gov/vuln/detail/CVE-2026-33846
• report
  https://access.redhat.com/security/cve/CVE-2026-42009