Description

Cua computer-server versions before 0.3.42 skip authentication when the CONTAINER_NAME environment variable is unset and bind to all interfaces by default, allowing unauthenticated attackers to execute arbitrary commands. Attackers can reach TCP port 8000 to run shell commands via the run_command endpoint, read and write arbitrary files through file operation endpoints, and access interactive PTY shells without authentication.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-05T10:16:43.463Z",
  "pubdate": "2026-09-05T10:16:43.463Z",
  "executiveSummary": "Cua computer-server versions prior to 0.3.42 are susceptible to a critical authentication bypass vulnerability, leading to unauthorized remote command execution and full system compromise.\nThe vulnerability originates from a logical flaw where the application fails to enforce authentication mechanisms when the 'CONTAINER_NAME' environment variable remains unset.\nBy default, the server binds to all network interfaces, exposing sensitive administrative endpoints on TCP port 8000 to any reachable network participant.\nAn unauthenticated attacker can exploit this condition to execute arbitrary shell commands, perform unauthorized read/write file operations, and gain interactive PTY shell access.\nThis vulnerability poses a severe risk, effectively granting full control over the host system. No authentication credentials are required for exploitation, making the system highly vulnerable to automated scanning and widespread remote attacks.",
  "technicalDetails": "The vulnerability in Cua computer-server (versions < 0.3.42) stems from a conditional logic failure within the authentication middleware. The application relies on the presence of the 'CONTAINER_NAME' environment variable to toggle authentication requirements. When this variable is unset, the authentication check is bypassed entirely for all incoming requests.\nFurthermore, the server default configuration binds the application service to all available network interfaces (0.0.0.0:8000), significantly increasing the attack surface by making it accessible to non-local network traffic. This configuration creates a direct pathway for unauthenticated actors to interact with protected API endpoints.\nThe attack flow proceeds as follows: First, the attacker identifies a reachable instance of Cua computer-server on TCP port 8000. Second, the attacker sends crafted HTTP requests to the 'run_command' endpoint. Because the authentication logic is bypassed due to the unset 'CONTAINER_NAME' environment variable, the server processes these requests without verifying the requester's identity. Third, the server executes the injected payload at the system level with the permissions of the application process.\nBeyond command execution, the attacker can leverage auxiliary file operation endpoints. These allow for arbitrary file read and write operations, enabling the attacker to exfiltrate sensitive configuration files, modify binaries, or upload malicious web shells to persist in the environment. Finally, the ability to spawn an interactive PTY shell provides the attacker with a persistent, bidirectional communication channel to the underlying operating system.\nThe impact of this vulnerability is total system compromise. The absence of privilege enforcement means that any commands executed by the attacker inherit the full privileges of the Cua server process. The ease of exploitation, combined with the lack of required authentication or specific user interaction, makes this a high-severity remote code execution flaw. The vulnerability effectively turns the intended management server into a remote backdoor, facilitating lateral movement and full data exfiltration."
}