Flowise, a drag‑and‑drop interface for building large language model flows, contains a flaw in its HTTP security module that fails to normalize IPv4‑mapped IPv6 addresses such as ::ffff:127.0.0.1 before checking them against a deny list. Because the CIDR parsing logic treats these addresses as IPv6 while the deny list contains IPv4 entries, the check is skipped and an attacker can cause the system to resolve a hostname to a private or cloud metadata IP. The weakness is classified as CWE-918 (Server Side Request Forgery) and CWE-1389 (IP Address Normalization Issues). This allows an attacker who can control DNS resolution for a hostname used by the application to force internal requests to localhost, internal services, or cloud metadata endpoints, potentially exposing sensitive data or enabling further compromise.

The vulnerability affects FlowiseAI's Flowise platform in all releases prior to version 3.1.3. No other product or vendor is listed as impacted.

The CVSS score of 7.6 indicates a high severity vulnerability. EPSS is not available, and the flaw is not in the CISA KEV catalog, suggesting limited but plausible exploitation. The attack vector is inferred to be remote, relying on the attacker’s ability to influence DNS lookups for hostnames that the Flowise application resolves. The vulnerability can be exploited by submitting a crafted hostname that resolves to an IPv4‑mapped IPv6 address pointing to an internal resource, thereby bypassing the intended deny‑list protection.