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Ubuntu Security Notice USN-6657-2
April 24, 2024

dnsmasq vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS (Available with Ubuntu Pro)
- Ubuntu 16.04 LTS (Available with Ubuntu Pro)

Summary:

Several security issues were fixed in Dnsmasq.

Software Description:
- dnsmasq: Small caching DNS proxy and DHCP/TFTP server

Details:

USN-6657-1 fixed several vulnerabilities in Dnsmasq. This update provides
the corresponding update for Ubuntu 16.04 LTS and Ubuntu 18.04 LTS.

Original advisory details:

 Elias Heftrig, Haya Schulmann, Niklas Vogel, and Michael Waidner discovered
 that Dnsmasq icorrectly handled validating DNSSEC messages. A remote
 attacker could possibly use this issue to cause Dnsmasq to consume
 resources, leading to a denial of service. (CVE-2023-50387)
 
 It was discovered that Dnsmasq incorrectly handled preparing an NSEC3
 closest encloser proof. A remote attacker could possibly use this issue to
 cause Dnsmasq to consume resources, leading to a denial of service.
 (CVE-2023-50868)
 
 It was discovered that Dnsmasq incorrectly set the maximum EDNS.0 UDP
 packet size as required by DNS Flag Day 2020. This issue only affected
 Ubuntu 23.10. (CVE-2023-28450)

Update instructions:

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

Ubuntu 18.04 LTS (Available with Ubuntu Pro):
  dnsmasq-base                    2.90-0ubuntu0.18.04.1+esm1

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
  dnsmasq-base                    2.90-0ubuntu0.16.04.1+esm1

This update uses a new upstream release, which includes additional bug
fixes. After a standard system update you need to reboot your computer to
make all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-6657-2
  https://ubuntu.com/security/notices/USN-6657-1
  CVE-2023-28450, CVE-2023-50387, CVE-2023-50868