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Ubuntu 26.04 LTS Kerberos Important DoS Issues USN-8585-1 CVE-2026-11850

ubuntu
Calendar Grey July 22, 2026
Scroller Ubuntu
Multiple security issues affecting Kerberos have been resolved in Ubuntu, addressing potential denial of service risks.
Several security issues were fixed in Kerberos.

Summary

Several security issues were fixed in Kerberos.

Software Description:

- krb5: MIT Kerberos Network Authentication Protocol

Details:

It was discovered that Kerberos had an integer underflow vulnerability

in the berval2tl_data() function. An attacker could possibly use this issue

to cause Kerberos to crash, resulting in a denial of service.

(CVE-2026-11850)

It was discovered that Kerberos had vulnerabilities in its NegoEx mechanism

parsing. A remote attacker could possibly use these issues to cause

Kerberos to crash, resulting in a denial of service. (CVE-2026-40355,

CVE-2026-40356)

Topics%20covered

Topics Covered

security advisory denial of service Ubuntu important krb5 integer underflow

Update Instructions

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
  krb5-admin-server               1.22.1-2ubuntu4.1
  krb5-kdc                        1.22.1-2ubuntu4.1
  libkrb5-3                       1.22.1-2ubuntu4.1

Ubuntu 24.04 LTS
  krb5-admin-server               1.20.1-6ubuntu2.7
  krb5-kdc                        1.20.1-6ubuntu2.7
  libkrb5-3                       1.20.1-6ubuntu2.7

Ubuntu 22.04 LTS
  krb5-admin-server               1.19.2-2ubuntu0.8
  krb5-kdc                        1.19.2-2ubuntu0.8
  libkrb5-3                       1.19.2-2ubuntu0.8

After a standard system update you need to restart Kerberos to make
all the necessary changes.

References

https://ubuntu.com/security/notices/USN-8585-1

CVE-2026-11850, CVE-2026-40355, CVE-2026-40356

Severity
important
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-8585-1

Topics%20covered

Topics Covered

security advisory denial of service Ubuntu important krb5 integer underflow

Package Information

https://launchpad.net/ubuntu/+source/krb5/1.22.1-2ubuntu4.1
https://launchpad.net/ubuntu/+source/krb5/1.20.1-6ubuntu2.7
https://launchpad.net/ubuntu/+source/krb5/1.19.2-2ubuntu0.8

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