CVE-2026-45366 typescript-utcp: SSRF via attacker-controlled OpenAPI servers[0].url in HTTP communication protocol
Attackers can force the library to make requests to internal services by hosting a malicious OpenAPI spec, bypassing URL validation checks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-45366?
CVE-2026-45366 is a medium-severity server-side request forgery vulnerability in universal-tool-calling-protocol typescript-utcp, published on 28 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
typescript-utcp is a typescript implementation of UTCP. Prior to 1.1.2, 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. This vulnerability is fixed in 1.1.2.
Weakness: CWE-918
Which versions are affected by CVE-2026-45366?
2 open source packages ship an affected version, including @utcp/http.
| Package | Affected | Fixed in |
|---|---|---|
@utcp/http npm | All versions | 1.1.2 |
@utcp/http npm | All versions | 1.1.2 |
How do I fix CVE-2026-45366?
Upgrade @utcp/http to 1.1.2 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-45366 being exploited?
There is no known exploitation of CVE-2026-45366 in the wild and no public exploit code.
Sources
Also known as GHSA-r8j5-8747-88cm.