Vulnerability · Published Aug 27, 2026 · Assigned by VulnCheck
CVE-2026-81098Telnyx MCP Server through 6.83.0 Missing Authentication on Streamable HTTP Transport
Critical 9.1
In plain English
A critical-severity missing authentication in telnyx-mcp from team-telnyx. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 54% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| team-telnyx | telnyx-mcp | 0 – through 6.83.0 |
Weakness: CWE-306 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
References
- https://github.com/team-telnyx/telnyx-node product
- https://github.com/team-telnyx/telnyx-node/pull/450 issue-tracking, patch
- GitHub Security Advisory (GHSA-46jp-xr2h-fw7h) vendor-advisory
- VulnCheck Advisory: Telnyx MCP Server through 6.83.0 Missing Authentication on Streamable HTTP Transport third-party-advisory