Samba Vulnerabilities — Ubuntu Security Update (USN-8621-1)

This is a security release for Ubuntu 20.04, Ubuntu 22.04. The fix ships in the current release line (referenced builds: 26.04, 24.04, 22.04, 23.6). Update the product on every affected server to the patched release — there is no workaround, and unpatched servers remain exposed until updated.

High 6.1 CVSS 2026-07-28

Ubuntu 20.04 Ubuntu 22.04

Fix Commands

Debian/Ubuntu

sudo apt update && sudo apt upgrade

What this means under a SharedLicense license

The advisory's own severity data peaks at CVSS 6.1 (CWE-732); unpatched Ubuntu 20.04, Ubuntu 22.04 servers remain exposed until updated.

It was discovered that Samba’s pam_winbind incorrectly handled home
directory ownership when mkhomedir was enabled. A local attacker could
possibly use this issue to cause a denial of service by triggering a change
in ownership of the root directory. (CVE-2026-15779)

Arjun Basnet, Douglas Bagnall, and Andrew Tridge…

Ubuntu Security Notices
USN-8621-1

Publication date

28 July 2026

Overview

Several security issues were fixed in Samba.

Releases

26.04 LTS

24.04 LTS

22.04 LTS

Packages

samba – SMB/CIFS file, print, and login server for Unix

Details

Arjun Basnet, Douglas Bagnall, and Andrew Tridgell discovered that Samba
incorrectly handled TSIG packets with name compression. A remote attacker
could possibly use this issue to cause Samba to crash, resulting in a
denial of service. (CVE-2026-6949)

Tristan Madani discovered that Samba incorrectly handled malformed ASN.1
kpasswd packets. An authenticated user could possibly use this issue to
cause Samba to crash, resulting in a denial of service. (CVE-2026-58216)

Andrew Tridgell and Tristan Madani discovered that Samba incorrectly
handled TKEY…

Andrew Tridgell and Tristan Madani discovered that Samba incorrectly
handled TKEY name registration. A remote attacker could possibly use this
issue to exhaust the TKEY name cache, resulting in a denial of service.
(CVE-2026-58218)

It was discovered that Samba incorrectly handled internal LDB special
directory names when processing authenticated LDAP requests. An
authenticated user could possibly use this issue to perform unauthorized
modifications and gain control of a domain. (CVE-2026-58221)

Andrew Tridgell and Tristan Madani discovered that Samba incorrectly
handled LDAP Compare requests. An authenticated user could possibly use
this issue to obtain sensitive information. (CVE-2026-58222)

Tristan Madani, Andrew Tridgell, and Martin Schwenke discovered that the
CTDB protocol in Samba had insufficient bounds checking. A remote attacker
could possibly use this issue to cause Samba to crash, resulting in a
denial of service. (CVE-2026-58224)

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Update instructions

In general, a standard system update will make all the necessary changes.

Learn more about how to get the fixes.

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

Ubuntu Release	Package Version
26.04 LTS resolute	samba – 2:4.23.6+dfsg-1ubuntu2.2
24.04 LTS noble	samba – 2:4.19.5+dfsg-4ubuntu9.7
22.04 LTS jammy	samba – 2:4.15.13+dfsg-0ubuntu1.13

References

Frequently Asked Questions

What does USN-8621-1 fix?

It was discovered that Samba's pam_winbind incorrectly handled home directory ownership when mkhomedir was enabled.

Which Ubuntu releases are covered?

Ubuntu 20.04, Ubuntu 22.04.

How do I apply it?

Standard package update (apt).

References

Security Advisories

Related Advisories

Linux Kernel (HWE) Vulnerabilities — Ubuntu Security Update (USN-9018-2)

2026-11-12

Tornado Regression — Ubuntu Security Update (USN-8952-3)

2026-11-11

Linux Kernel (Azure CVM) Vulnerabilities — Ubuntu Security Update (USN-9039-1)

2026-11-11

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