@utcp/http: SSRF via attacker-controlled OpenAPI servers[0].url in HTTP communication protocol
Date: 2026-05
Affected: npm/@utcp/http
Attack vector: prompt-injection
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-45366
CWE: CWE-918
CVSS: 4.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N)

## Summary The `@utcp/http` package is vulnerable to a blind Server-Side Request Forgery (SSRF) caused by a trust-boundary inconsistency between manual discovery and tool invocation. `registerManual()` validates the discovery URL against an HTTPS / loopback allowlist, but `callTool()` reuses the resolved `toolCallTemplate.url` directly without revalidating, and the `OpenApiConverter` blindly trusts whatever `servers[0].url` an attacker-hosted spec declares. An attacker who hosts a malicious OpenAPI spec on a legitimate HTTPS endpoint can declare e.g. `servers: [{ url: "http://127.0.0.1:9090" }]` or `servers: [{ url: "http://169.254.169.254" }]`; the converter then produces tools whose URL points at internal services on the agent host. A separate prefix-bypass also affected the discovery-time check: the previous `startsWith('http://localhost')` guard let URLs like `http://localhost.evil.com` through. ## Sister advisory This is the npm/TypeScript counterpart of [GHSA-39j6-4867-gg4w / CVE-2026-44661](https://github.com/universal-tool-calling-protocol/python-utcp/security/advisories/GHSA-39j6-4867-gg4w) on the Python `utcp-http` package. Same vulnerability, same fix shape, same reporter. ## Versions and patch state - `@utcp/http <= 1.1.1` — vulnerable. Both the loopback-redirect (`http://127.0.0.1`) and the non-loopback internal-IP variants (e.g. `http://169.254.169.254`, `http://10.0.0.5`) succeed. Note: the `streamable_http` and `sse` `callToolStreaming` paths in 1.1.1 ar


Mitigations:

Architectural layers (MAESTRO):