Vulnerability in Universal-Tool-Calling-Protocol Python-Utcp
CVE-2026-101057
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.
Published .
CVSS v3 metric
CVSS v3 base score 3.1 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/universal-tool-calling-protocol/python-utcp/security/advisories/GHSA… (vendor-advisory)
- www.vulncheck.com/advisories/utcp-mcp-before-1.1.3-ssrf-via-unvalidated-mcp-ser… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-101057?
- CVE-2026-101057 is a low-severity vulnerability in Universal-Tool-Calling-Protocol Python-Utcp, classified under Cleartext Transmission of Sensitive Information. CVSS score: 3.1/10. Published 2026-09-27.
- How severe is CVE-2026-101057?
- Low severity. CVSS v3 base score is 3.1 out of 10.