RHSA-2026:24683HighCVSS 5.9

Red Hat Security Advisory: krb5 security update

Published
June 9, 2026
Last Modified
August 21, 2026

🔗 CVE IDs covered (1)

CVE-2026-40356 →

📋 Description

CVE-2026-40356 — krb5: MIT Kerberos 5 (krb5): Denial of Service via integer underflow and out-of-bounds read

🎯 Affected products117

  • Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-0:1.21.1-8.el9_6.2.src as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.aarch64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.i686 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.i686 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.ppc64le as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.s390x as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debuginfo-0:1.21.1-8.el9_6.2.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.aarch64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.i686 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.i686 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.ppc64le as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.s390x as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-debugsource-0:1.21.1-8.el9_6.2.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-devel-0:1.21.1-8.el9_6.2.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-devel-0:1.21.1-8.el9_6.2.i686 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-devel-0:1.21.1-8.el9_6.2.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-devel-0:1.21.1-8.el9_6.2.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-devel-0:1.21.1-8.el9_6.2.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.6)
  • krb5-libs-0:1.21.1-8.el9_6.2.aarch64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • krb5-libs-0:1.21.1-8.el9_6.2.i686 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.6)
  • +87 more not shown

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 Workaround: To mitigate this issue, ensure that the NegoEx mechanism is not registered in the `/etc/gss/mech` configuration file. Removing the corresponding entry from this file will prevent the vulnerable code path from being activated. This action may impact services that rely on the NegoEx GSS-API mechanism. A restart of affected Kerberos-dependent services may be required for the change to take effect.

🔗 References (4)