CVE-2026-58395: medium-severity vulnerability in opnsense core

OPNsense is a FreeBSD based firewall and routing platform. Prior to version 26.1.11, the safe-delete path reached through ApiMutableModelControllerBase::delBase() interpolates an unvalidated safe-delete token from the request URL into an XPath expression over config.xml before confirming that the token is a valid identifier. A user holding any one affected module privilege can send a crafted token to one of 21 affected delete endpoints covering Traffic Shaper, DHCP relay, Dnsmasq, Firewall Category, or Kea DHCP, causing the XPath to match configuration data across modules. The resulting error response exposes configuration item names, descriptions, reference paths, and UUIDs and provides an XPath substring-presence oracle, including for modules the user cannot otherwise access. The request does not modify configuration or perform a deletion. This issue is fixed in version 26.1.11.