Auth bypass in Team-Telnyx Telnyx-Mcp
CVE-2026-81098
The Telnyx MCP server exposed its HTTP transport on every interface and did not require a caller credential. packages/mcp-server/src/http.ts served MCP on the root path with a listener bound to all interfaces and parsed the caller's authentication headers in a mode that did not fail when they were absent, so a request without any credential completed initialisation and dispatched tools. Dispatch forwarded the server's own stored credentials, the Telnyx API key and client secret together with the code-execution key, to the upstream endpoint, so an unauthenticated caller able to reach the port acted with them. The current code defaults the host to loopback, requires a server API key, and enforces it in middleware.
Vulnerability class: Broken Authentication
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
Affected products
Weakness classification (CWE)
References
- disclosure@vulncheck.com (product)
- disclosure@vulncheck.com (issue-tracking)
- disclosure@vulncheck.com (vendor-advisory)
- disclosure@vulncheck.com (third-party-advisory)
Frequently asked questions
- What is CVE-2026-81098?
- CVE-2026-81098 is a critical-severity vulnerability in Team-Telnyx Telnyx-Mcp, classified under Missing Authentication for Critical Function. CVSS score: 9.1/10. Published 2026-08-27.
- How severe is CVE-2026-81098?
- Critical severity. CVSS v3 base score is 9.1 out of 10.