Flowise's HTTP security module (httpSecurity.ts) did not normalize IPv4-mapped IPv6 addresses (e.g., ::ffff:127.0.0.1) before checking against the deny list. Because ipaddr.js treats these as IPv6 addresses, IPv4 CIDR deny-list checks were skipped. An attacker who controls DNS resolution for hostnames used by HTTP Node, API Chain, Document Loader, MCP tool, or other components using secureAxiosRequest(), secureFetch(), or checkDenyList() could return a AAAA record with an IPv4-mapped IPv6 address. This causes requests to reach protected internal endpoints such as localhost or cloud metadata services. The vulnerability is resolved in Flowise version 3.1.3.

An attacker with the ability to control DNS resolution can bypass IP deny lists and cause the application to send requests to internal or sensitive endpoints, potentially exposing internal services or cloud metadata. This can lead to unauthorized information disclosure or further internal network attacks. The CVSS 4.0 score is 7.6 (high severity), reflecting network attack vector, low attack complexity, and partial privileges required.

Upgrade Flowise to version 3.1.3 or later, where this vulnerability is fixed by proper normalization of IPv4-mapped IPv6 addresses before deny list checks. No other mitigations are specified or required.