EUVD-2026-67026
GHSA-j929-p4w2-gfw7
Severity by source
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Reachable HTTP port with no credential accepted gives AV:N/AC:L/PR:N/UI:N; theft and reuse of stored API keys yields high C and I, no availability impact.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3DescriptionCVE.org
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.
AnalysisAI
Authentication bypass in the Telnyx MCP server (team-telnyx/telnyx-node, through 6.83.0) lets any network-reachable caller invoke MCP tools with no credential. The Streamable HTTP transport bound to all interfaces and parsed auth headers in a non-failing mode, so a request lacking credentials still completed initialisation and dispatched tools - which then forwarded the server's own stored Telnyx API key, client secret, and code-execution key upstream. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the server to be running the Streamable HTTP transport (rather than the default stdio transport) with the vulnerable all-interfaces bind in versions through 6.83.0, and the attacker must have network reachability to that listening port. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N, score 9.3) aligns tightly with the description: remote, low-complexity, no authentication, no user interaction, with high confidentiality and integrity impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who can reach the MCP HTTP port - for example on a shared host, an exposed container port, or a flat internal network - sends an MCP initialise and tool-dispatch request with no authentication headers. The server accepts it and executes the requested tools against the upstream Telnyx API using its own stored API key and code-execution key, letting the attacker abuse the victim's telecom account. … |
| Remediation | Upgrade to the fixed release published after 6.83.0 that incorporates PR #450 (https://github.com/team-telnyx/telnyx-node/pull/450) and GHSA-46jp-xr2h-fw7h; the corrected code defaults the host to loopback, requires a server API key, and enforces it in middleware. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Audit your environment for deployments of team-telnyx/telnyx-node versions through 6.83.0; if present, immediately restrict network access to the MCP server via firewall rules to trusted internal networks only. …
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Same technique Authentication Bypass
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External POC / Exploit Code
Leaving vuln.today