CVE-2026-81098

Telnyx MCP Server through 6.83.0 Missing Authentication on Streamable HTTP Transport

Published Aug 27, 2026 CVSS 4.0 · 9.3 Critical EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Telnyx
Telnyx telnyx-mcp
Vendors & Products Telnyx
Telnyx telnyx-mcp
Type Values Removed Values Added
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.
Title Telnyx MCP Server through 6.83.0 Missing Authentication on Streamable HTTP Transport
Weaknesses CWE-306
References
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

cvssV4_0

{'score': 9.3, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Aug 29, 2026, 11:48 AM
Reserved
Aug 26, 2026, 4:00 PM
Status
Deferred
Published
Aug 27, 2026, 5:20 PM
Modified
Sep 24, 2026, 8:43 PM