Issued:

2026-05-19

Updated:

2026-05-19

RHSA-2026:19145 - Important: krb5 security update

Synopsis

Important: krb5 security update

Type/Severity

Security Advisory Important

Topic

An update for krb5 is now available for Red Hat Enterprise Linux 10.

Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

Kerberos is a network authentication system, which can improve the security of your network by eliminating the insecure practice of sending passwords over the network in unencrypted form. It allows clients and servers to authenticate to each other with the help of a trusted third party, the Kerberos key distribution center (KDC).

Security Fix(es):

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

• krb5: MIT Kerberos 5: Denial of Service via NULL pointer dereference in NegoEx mechanism (CVE-2026-40355)

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.

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

Affected Products

Updated Packages

• krb5-devel-1.21.3-10.el10_2.x86_64.rpm
• krb5-pkinit-1.21.3-10.el10_2.ppc64le.rpm
• krb5-devel-1.21.3-10.el10_2.aarch64.rpm
• krb5-libs-debuginfo-1.21.3-10.el10_2.s390x.rpm
• libkadm5-debuginfo-1.21.3-10.el10_2.s390x.rpm
• krb5-server-debuginfo-1.21.3-10.el10_2.x86_64.rpm
• krb5-debuginfo-1.21.3-10.el10_2.aarch64.rpm
• krb5-devel-1.21.3-10.el10_2.s390x.rpm
• libkadm5-1.21.3-10.el10_2.aarch64.rpm
• krb5-server-1.21.3-10.el10_2.s390x.rpm
• krb5-debugsource-1.21.3-10.el10_2.x86_64.rpm
• libkadm5-debuginfo-1.21.3-10.el10_2.ppc64le.rpm
• krb5-debugsource-1.21.3-10.el10_2.ppc64le.rpm
• krb5-libs-1.21.3-10.el10_2.s390x.rpm
• krb5-server-1.21.3-10.el10_2.aarch64.rpm
• krb5-libs-1.21.3-10.el10_2.ppc64le.rpm
• krb5-server-debuginfo-1.21.3-10.el10_2.aarch64.rpm
• krb5-xrealmauthz-1.21.3-10.el10_2.aarch64.rpm
• krb5-pkinit-1.21.3-10.el10_2.s390x.rpm
• krb5-libs-1.21.3-10.el10_2.x86_64.rpm
• krb5-xrealmauthz-1.21.3-10.el10_2.ppc64le.rpm
• krb5-devel-1.21.3-10.el10_2.ppc64le.rpm
• krb5-debuginfo-1.21.3-10.el10_2.ppc64le.rpm
• krb5-server-1.21.3-10.el10_2.x86_64.rpm
• krb5-server-ldap-debuginfo-1.21.3-10.el10_2.aarch64.rpm
• krb5-1.21.3-10.el10_2.src.rpm
• krb5-server-ldap-1.21.3-10.el10_2.ppc64le.rpm
• krb5-workstation-debuginfo-1.21.3-10.el10_2.ppc64le.rpm
• krb5-workstation-1.21.3-10.el10_2.x86_64.rpm
• krb5-libs-debuginfo-1.21.3-10.el10_2.aarch64.rpm
• krb5-pkinit-debuginfo-1.21.3-10.el10_2.ppc64le.rpm
• krb5-server-ldap-1.21.3-10.el10_2.x86_64.rpm
• libkadm5-1.21.3-10.el10_2.x86_64.rpm
• krb5-server-debuginfo-1.21.3-10.el10_2.s390x.rpm
• krb5-pkinit-debuginfo-1.21.3-10.el10_2.aarch64.rpm
• krb5-server-ldap-debuginfo-1.21.3-10.el10_2.s390x.rpm
• krb5-pkinit-1.21.3-10.el10_2.aarch64.rpm
• krb5-debuginfo-1.21.3-10.el10_2.x86_64.rpm
• krb5-xrealmauthz-debuginfo-1.21.3-10.el10_2.s390x.rpm
• krb5-debugsource-1.21.3-10.el10_2.aarch64.rpm
• libkadm5-1.21.3-10.el10_2.ppc64le.rpm
• krb5-workstation-debuginfo-1.21.3-10.el10_2.aarch64.rpm
• krb5-debugsource-1.21.3-10.el10_2.s390x.rpm
• krb5-workstation-1.21.3-10.el10_2.aarch64.rpm
• krb5-workstation-1.21.3-10.el10_2.s390x.rpm
• krb5-xrealmauthz-1.21.3-10.el10_2.s390x.rpm
• libkadm5-debuginfo-1.21.3-10.el10_2.x86_64.rpm
• krb5-debuginfo-1.21.3-10.el10_2.s390x.rpm
• krb5-libs-debuginfo-1.21.3-10.el10_2.x86_64.rpm
• krb5-server-ldap-debuginfo-1.21.3-10.el10_2.ppc64le.rpm
• krb5-libs-1.21.3-10.el10_2.aarch64.rpm
• krb5-server-ldap-debuginfo-1.21.3-10.el10_2.x86_64.rpm
• krb5-xrealmauthz-debuginfo-1.21.3-10.el10_2.ppc64le.rpm
• krb5-workstation-debuginfo-1.21.3-10.el10_2.x86_64.rpm
• krb5-libs-debuginfo-1.21.3-10.el10_2.ppc64le.rpm
• krb5-server-ldap-1.21.3-10.el10_2.s390x.rpm
• krb5-workstation-1.21.3-10.el10_2.ppc64le.rpm
• libkadm5-debuginfo-1.21.3-10.el10_2.aarch64.rpm
• krb5-pkinit-debuginfo-1.21.3-10.el10_2.x86_64.rpm
• krb5-server-1.21.3-10.el10_2.ppc64le.rpm
• krb5-workstation-debuginfo-1.21.3-10.el10_2.s390x.rpm
• krb5-xrealmauthz-1.21.3-10.el10_2.x86_64.rpm
• krb5-pkinit-debuginfo-1.21.3-10.el10_2.s390x.rpm
• krb5-pkinit-1.21.3-10.el10_2.x86_64.rpm
• krb5-server-debuginfo-1.21.3-10.el10_2.ppc64le.rpm
• krb5-xrealmauthz-debuginfo-1.21.3-10.el10_2.aarch64.rpm
• krb5-xrealmauthz-debuginfo-1.21.3-10.el10_2.x86_64.rpm
• libkadm5-1.21.3-10.el10_2.s390x.rpm
• krb5-server-ldap-1.21.3-10.el10_2.aarch64.rpm

Fixes

• This content is not included.BZ - 2463368
• This content is not included.BZ - 2463370

CVEs

• CVE-2026-40355
• CVE-2026-40356

References

• https://access.redhat.com/security/updates/classification/#important

Additional information

• The Red Hat security contact is This content is not included.secalert@redhat.com. More contact details at Security Contacts and Procedures.
• Offline Security Data data is available for integration with other systems. See Offline Security Data API to get started.