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...