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Ubuntu Security Notice USN-3816-3
November 27, 2018

systemd regression
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A security issue affects these releases of Ubuntu and its derivatives:

– Ubuntu 16.04 LTS

Summary:

USN-3816-1 caused a regression in systemd-tmpfiles.

Software Description:
– systemd: system and service manager

Details:

USN-3816-1 fixed vulnerabilities in systemd. The fix for CVE-2018-6954
caused a regression in systemd-tmpfiles when running Ubuntu inside a
container on some older kernels. This issue only affected Ubuntu 16.04
LTS. In order to continue to support this configuration, the fixes for
CVE-2018-6954 have been reverted.

We apologize for the inconvenience.

Original advisory details:

 Jann Horn discovered that unit_deserialize incorrectly handled status
messages
 above a certain length. A local attacker could potentially exploit this via
 NotifyAccess to inject arbitrary state across re-execution and obtain root
 privileges. (CVE-2018-15686)
 
 Jann Horn discovered a race condition in chown_one(). A local attacker
 could potentially exploit this by setting arbitrary permissions on certain
 files to obtain root privileges. This issue only affected Ubuntu 18.04 LTS
 and Ubuntu 18.10. (CVE-2018-15687)
 
 It was discovered that systemd-tmpfiles mishandled symlinks in
 non-terminal path components. A local attacker could potentially exploit
 this by gaining ownership of certain files to obtain root privileges. This
 issue only affected Ubuntu 16.04 LTS and Ubuntu 18.04 LTS. (CVE-2018-6954)

Update instructions:

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

Ubuntu 16.04 LTS:
  systemd                         229-4ubuntu21.10

After a standard system update you need to reboot your computer to make
all the necessary changes.

References:
  https://usn.ubuntu.com/usn/usn-3816-3
  https://usn.ubuntu.com/usn/usn-3816-1
  https://launchpad.net/bugs/1804847

Package Information:
  https://launchpad.net/ubuntu/+source/systemd/229-4ubuntu21.10

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