CVE-2026-84201: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in argneshu appium-mcp-server

The appium-mcp-server application through version 0.1.61 does not properly validate or normalize file paths in its write_file and write_files_batch tools. This improper limitation of pathname allows attackers to perform path traversal attacks by providing absolute paths or relative paths containing parent directory segments. Consequently, attackers can write files outside the designated PROJECT_ROOT directory, potentially overwriting critical files such as shell profiles and configuration files in the home directory, using the server user's privileges.

Successful exploitation allows an attacker with limited privileges to overwrite arbitrary files on the server filesystem, including sensitive configuration and shell profile files. This can lead to unauthorized modification of server behavior or persistence mechanisms, potentially escalating impact depending on the server user's privileges. The CVSS 4.0 score is 6.9 (medium severity), reflecting local attack vector with low complexity and no privileges required but requiring user interaction.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict access to the vulnerable write_file and write_files_batch functionality and monitor for suspicious file modifications. Avoid running the server with excessive privileges to limit potential damage.