1. Ubuntu Security Notices
  2. USN-4510-1

USN-4510-1: Samba vulnerability

Publication date

17 September 2020

Overview

Samba would allow unintended access to files over the network.

Releases

Packages

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

Details

Tom Tervoort discovered that the Netlogon protocol implemented by Samba
incorrectly handled the authentication scheme. A remote attacker could use
this issue to forge an authentication token and steal the credentials of
the domain admin.

This update fixes the issue by changing the “server schannel” setting to
default to “yes”, instead of “auto”, which will force a secure netlogon
channel. This may result in compatibility issues with older devices. A
future update may allow a finer-grained control over this setting.

Tom Tervoort discovered that the Netlogon protocol implemented by Samba
incorrectly handled the authentication scheme. A remote attacker could use
this issue to forge an authentication token and steal the credentials of
the domain admin.

This update fixes the issue by changing the “server schannel” setting to
default to “yes”, instead of “auto”, which will force a secure netlogon
channel. This may result in compatibility issues with older devices. A
future update may allow a finer-grained control over this setting.

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
18.04 bionic samba –  2:4.7.6+dfsg~ubuntu-0ubuntu2.19
16.04 xenial samba –  2:4.3.11+dfsg-0ubuntu0.16.04.30

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References

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