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    CVE-2026-42013

    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 certificate validation, potentially leading to spoofing or man-in-the-middle attacks.

    Published:May 26, 2026
    Last Modified:Sep 3, 2026
    EPS:May 26, 2026
    EPSS Score:0.00423
    CVSS Score:8.2

    Affected Products

    Vendor
    Gnu
    Product
    Gnutls
    Vendor
    Redhat
    Product
    Discovery
    Vendor
    Redhat
    Product
    Enterprise Linux
    Vendor
    Redhat
    Product
    Enterprise Linux Eus
    Vendor
    Redhat
    Product
    Hardened Images
    Vendor
    Redhat
    Product
    Hummingbird
    Vendor
    Redhat
    Product
    Openshift
    Vendor
    Redhat
    Product
    Openshift Container Platform
    Vendor
    Redhat
    Product
    Rhel Aus
    Vendor
    Redhat
    Product
    Rhel E4s
    Vendor
    Redhat
    Product
    Rhel Els
    Vendor
    Redhat
    Product
    Rhel Eus
    Vendor
    Redhat
    Product
    Rhel Eus Long Life
    Vendor
    Redhat
    Product
    Rhel Tus
    Vendor
    Redhat
    Product
    Rhui

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-295 Improper Certificate Validation

    Related CVEs

    CVE-2026-42014 (CVSS 6.6) — A flaw was found in GnuTLS. The `gnutls_pkcs11_token_set_pin` function, used for changing the Security Officer…
    CVE-2026-5419 (CVSS 3.7) — A flaw was found in gnutls. The PKCS#7 padding check, performed during decryption, was not constant-time. This…
    CVE-2026-42012 (CVSS 7.1) — A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially craft…
    CVE-2026-5260 (CVSS 8.2) — A flaw was found in libgnutls. A remote attacker, by sending an extremely short premaster secret during an RSA…
    CVE-2026-33846 (CVSS 7.5) — A heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The iss…
    CVE-2026-3832 (CVSS 3.7) — A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially craft…
    CVE-2026-33845 (CVSS 7.5) — A flaw in GnuTLS DTLS handshake parsing allows malformed fragments with zero length and non-zero offset, leadi…
    CVE-2026-3833 (CVSS 6.5) — A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of `n…
    CVE-2026-42009 (CVSS 7.5) — A flaw was found in gnutls. A remote attacker could exploit an issue in the Datagram Transport Layer Security …
    CVE-2026-42010 (CVSS 7.1) — A flaw was found in gnutls. Servers configured with RSA-PSK (Rivest–Shamir–Adleman – Pre-Shared Key) wrongfull…

    References

    https://access.redhat.com/errata/RHSA-2026:13274
    https://access.redhat.com/errata/RHSA-2026:20611
    https://access.redhat.com/errata/RHSA-2026:20612
    https://access.redhat.com/errata/RHSA-2026:20613
    https://access.redhat.com/errata/RHSA-2026:26319
    https://access.redhat.com/errata/RHSA-2026:26409
    https://access.redhat.com/errata/RHSA-2026:29197
    https://access.redhat.com/errata/RHSA-2026:30004
    https://access.redhat.com/errata/RHSA-2026:30849
    https://access.redhat.com/errata/RHSA-2026:30850
    https://access.redhat.com/errata/RHSA-2026:32962
    https://access.redhat.com/errata/RHSA-2026:33125
    https://access.redhat.com/errata/RHSA-2026:40762
    https://access.redhat.com/errata/RHSA-2026:41921
    https://access.redhat.com/errata/RHSA-2026:43575
    https://access.redhat.com/errata/RHSA-2026:56853
    https://access.redhat.com/errata/RHSA-2026:57483
    https://access.redhat.com/errata/RHSA-2026:58981
    https://access.redhat.com/errata/RHSA-2026:59831
    https://access.redhat.com/errata/RHSA-2026:60019
    https://access.redhat.com/security/cve/CVE-2026-42013
    https://bugzilla.redhat.com/show_bug.cgi?id=2467448
    https://www.gnutls.org/security-new.html#GNUTLS-SA-2026-04-29-8

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High