Fedora 42 krb5 Moderate NegoEx DoS Fix Advisory FEDORA-2026-6c99aaa6d3
fedora
May 14, 2026
Fix NegoEx parsing vulnerabilities (CVE-2026-40355, CVE-2026-40356)
Summary
Kerberos V5 is a trusted-third-party network authentication system,
which can improve your network's security by eliminating the insecure
practice of sending passwords over the network in unencrypted form.
Update Information:
Fix NegoEx parsing vulnerabilities (CVE-2026-40355, CVE-2026-40356)
Topics Covered
Change Log
* Wed Apr 29 2026 Julien Rische
References
[ 1 ] Bug #2463395 - CVE-2026-40356 krb5: MIT Kerberos 5 (krb5): Denial of Service via integer underflow and out-of-bounds read [fedora-all]
https://bugzilla.redhat.com/show_bug.cgi?id=2463395
[ 2 ] Bug #2463398 - CVE-2026-40355 krb5: MIT Kerberos 5: Denial of Service via NULL pointer dereference in NegoEx mechanism [fedora-all]
https://bugzilla.redhat.com/show_bug.cgi?id=2463398
Update Instructions
This update can be installed with the "dnf" update program. Use su -c 'dnf upgrade --advisory FEDORA-2026-6c99aaa6d3' at the command line. For more information, refer to the dnf documentation available at http://dnf.readthedocs.io/en/latest/command_ref.html#upgrade-command-label
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Severity
important
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Critical
Name: krb5
Product: Fedora 42
Version: 1.21.3
Release: 7.fc42
Summary: The Kerberos network authentication system
Topics Covered
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