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Ubuntu Security Notice USN-4969-3
June 07, 2021

isc-dhcp regression
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04

Summary:

USN-4969-1 introduced a regression in DHCP.

Software Description:
- isc-dhcp: DHCP server and client

Details:

USN-4969-1 fixed a vulnerability in DHCP. The package for Ubuntu 21.04
introduced a regression causing it to reject certain valid configuration
files. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

 Jon Franklin and Pawel Wieczorkiewicz discovered that DHCP incorrectly
 handled lease file parsing. A remote attacker could possibly use this issue
 to cause DHCP to crash, resulting in a denial of service.

Update instructions:

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

Ubuntu 21.04:
  isc-dhcp-client                 4.4.1-2.2ubuntu6.2
  isc-dhcp-server                 4.4.1-2.2ubuntu6.2

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

References:
  https://ubuntu.com/security/notices/USN-4969-3
  https://ubuntu.com/security/notices/USN-4969-1
  https://launchpad.net/bugs/1930917

Package Information:
  https://launchpad.net/ubuntu/+source/isc-dhcp/4.4.1-2.2ubuntu6.2