CVE-2026-19538 Bypass of BLOCKED ACL items on proxy protocol port over TCP or TLS

The BLOCKED access control list items that are evaluated to deny access on the the proxy protocol port can be bypassed completely when connecting over TCP or TLS and sending the query twice on connection that is kept open...

CVE-2026-19538

This vulnerability affects NSD (NLnet Labs' DNS server daemon). BLOCKED access control list items on the proxy protocol port can be completely bypassed by connecting over TCP or TLS and sending the query twice on a single kept-open connection. The CVSS 4.0 score is 8.2 (HIGH) , with primary impac...

CVE-2026-54478

A flaw was found in Unbound. When Unbound is configured to listen on a proxy-protocol port with DNS cookies enabled, it incorrectly computes the server cookie using the proxy's network address instead of the actual client's address. This vulnerability allows an off-path attacker to harvest a vali...

CVE-2026-54478

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...

CVE-2026-54478

CVE-2026-54478 affects NLnet Labs Unbound 1.18.0–1.25.1 when listening on a proxy-protocol-port with answer-cookie enabled. The RFC 9018 server-cookie (SipHash) is computed over the proxy’s wire address rather than the PROXYv2-declared client, causing a server cookie to validate for every PROXYv2...

CVE-2026-54478

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...