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CVSS 10.0CVSS 10.0 · CRITICAL

CVE-2026-81735Unauthenticated RCE in mcp-http-server

startServer.ts in the mcp-http-server package of UI-TARS-desktop defaulted its listen address to '::' when no host was given, so startSseAndStreamableHttpMcpServer bound the Streamable HTTP and SSE MCP transports to every interface, and its authentication middleware was optional: middlewares are applied only when a caller supplies them. The @agent-infra/mcp-server-commands and @agent-infra/mcp-server-filesystem entry points call startSseAndStreamableHttpMcpServer with a host and port alone and pass no middleware, so neither server required a credential. The commands server exposes a run_command tool that hands its caller-supplied command string to promisify(child_process.exec), so any unauthenticated client able to reach the port could run arbitrary commands as the user running the server, and the filesystem server exposed its file read and write tools on the same terms. The listen default became 127.0.0.1 in commit c2ad42e3eb9b27830db41a3e6f51ca7179d9b168; the package version stayed at 1.2.4 across that change, so the boundary is the commit rather than a release.

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Analysis

El paquete mcp-http-server en infraestructuras de UI-TARS vincula servicios a todas las interfaces de red sin autenticación obligatoria por defecto. Esto permite que cualquier atacante remoto ejecute comandos arbitrarios en el sistema operativo mediante el transporte de comandos expuesto, comprometiendo totalmente el equipo donde corre el servidor.

Relevant roles

BackendTypescriptJavascriptaiIAciberseguridad

Severity

Score: 10.0(CRITICAL)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
AV: NETWORK
AC: LOW
PR: NONE
UI: NONE
S: CHANGED
C: HIGH
I: HIGH
A: HIGH
Weakness (CWE): CWE-306

EPSS

No EPSS score yet (CVE may be too fresh).

Technical description

startServer.ts in the mcp-http-server package of UI-TARS-desktop defaulted its listen address to '::' when no host was given, so startSseAndStreamableHttpMcpServer bound the Streamable HTTP and SSE MCP transports to every interface, and its authentication middleware was optional: middlewares are applied only when a caller supplies them. The @agent-infra/mcp-server-commands and @agent-infra/mcp-server-filesystem entry points call startSseAndStreamableHttpMcpServer with a host and port alone and pass no middleware, so neither server required a credential. The commands server exposes a run_command tool that hands its caller-supplied command string to promisify(child_process.exec), so any unauthenticated client able to reach the port could run arbitrary commands as the user running the server, and the filesystem server exposed its file read and write tools on the same terms. The listen default became 127.0.0.1 in commit c2ad42e3eb9b27830db41a3e6f51ca7179d9b168; the package version stayed at 1.2.4 across that change, so the boundary is the commit rather than a release.

Published: 8/27/2026, 5:21:03 PM
Last modified: 8/27/2026, 5:21:03 PM

References

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