Dnsmasq: dnsmasq: --leasequery without address argument applies no source address check

Overview

A flaw was found in dnsmasq. When DHCP leasequery is enabled without listing allowed source addresses, the server does not check who sent the query. A host on the local network can request DHCP lease records and learn assigned addresses, MAC addresses, hostnames, and related lease metadata. The feature is off unless an administrator turns it on.

Affected

• rhceph/alloy-rhel10 (all versions)
• dnsmasq (all versions)
• dnsmasq (all versions)
• dnsmasq (all versions)
• dnsmasq (all versions)
• dnsmasq (all versions)
• openshift4/ose-baremetal-runtimecfg-rhel8 (all versions)
• openshift4/ose-baremetal-runtimecfg-rhel9 (all versions)
• openshift/ose-rhel-coreos-8 (all versions)
• openshift/ose-rhel-coreos-9 (all versions)
• openshift5/ose-baremetal-runtimecfg-rhel9 (all versions)
• openshift/ose-rhel-coreos-9 (all versions)
• dnsmasq (all versions)
• rhoso-operators/infra-rhel9-operator (all versions)

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Workarounds

The following measures reduce risk:

1. Prefer --leasequery=<addr>[/prefix] so only designated relays may query.
2. If leasequery is not needed, do not enable it. It is off by default.
3. If unrestricted leasequery is required, use firewall rules to limit which hosts can send DHCP packets to dnsmasq.