CVE-2026-101057 utcp-mcp before 1.1.3 SSRF via unvalidated MCP server URL
An attacker with control over operator-authored configurations can force the library to connect to internal hosts via unvalidated URLs, bypassing security 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
- None listed
What is CVE-2026-101057?
CVE-2026-101057 is a low-severity server-side request forgery vulnerability in universal-tool-calling-protocol python-utcp, published on 27 Sep 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
utcp-mcp (the MCP plugin of python-utcp) through 1.1.2 connects to the HTTP and WebSocket MCP server URLs given in a call template's mcpServers configuration without the ensure_secure_url validation that the HTTP-family plugins apply, so the HTTPS/WSS-or-loopback rule is not enforced. A call template naming a plain-HTTP, non-loopback MCP server URL is dialed as configured, exposing the MCP handshake to network interception and permitting cleartext connections to internal hosts. The mcpServers configuration is operator-authored rather than remote data, and the connection is an MCP handshake rather than an arbitrary request returning a body, which limits practical exploitation; the OAuth2 token_url credential path described in the original report was not reachable in the affected versions, because the OAuth2 handler was never invoked and the call template's auth field was not read. Fixed in utcp-mcp 1.1.3, which validates server URLs before any connection is made.
Weakness: CWE-319
Which versions are affected by CVE-2026-101057?
How do I fix CVE-2026-101057?
No fix has been published for CVE-2026-101057 yet. Limit exposure of the affected software until one is available.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-101057 being exploited?
There is no known exploitation of CVE-2026-101057 in the wild and no public exploit code.
Sources
Also known as GHSA-vr54-j4qq-9vj9.