CVE-2026-81098 PUBLISHED

Telnyx MCP Server through 6.83.0 Missing Authentication on Streamable HTTP Transport

Assigner: VulnCheck
Reserved: 26.08.2026 Published: 27.08.2026 Updated: 27.08.2026

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.

Metrics

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS Score: 9.3

Product Status

Vendor team-telnyx
Product telnyx-mcp
Versions Default: unaffected
  • affected from 0 to 6.83.0 (incl.)

Credits

  • Avishai Gonen (Pluto Security) finder

References

Problem Types

  • Missing Authentication for Critical Function CWE