CVE-2026-54478

Popis

In NLnet Labs Unbound 1.18.0 up to and including 1.25.1, when Unbound listens on a -proxy-protocol-port- interface with -answer-cookie: yes-, the RFC 9018 server-cookie SipHash is computed over the proxy-s wire address instead of the PROXYv2-declared client. One server cookie obtained through a given proxy node therefore validates for every PROXYv2-declared source behind that node. On a UDP+proxy-protocol front, an off-path attacker can harvest one cookie with a single legitimate query, then replay it under any spoofed source and pass DNS Cookie checks that were deployed to defeat this in the first place.