The chrome-devtools-mcp daemon writes its PID file using fs.writeFileSync() to a deterministic runtime path, typically /tmp/chrome-devtools-mcp-<uid>/daemon.pid on macOS and Linux when $XDG_RUNTIME_DIR is unset. Because the write operation does not use the O_NOFOLLOW flag, a local low-privilege user can pre-create the daemon.pid file as a symbolic link to another writable file owned by the victim user. When the daemon starts, it follows the symlink and overwrites the target file with the PID string, causing unintended truncation. This is a CWE-59 (Improper Link Resolution Before File Access) vulnerability affecting versions >=0.20.0 and <1.1.0. The vulnerability is fixed in version 1.1.0.

The vulnerability allows a local low-privilege user on the same POSIX host to cause the chrome-devtools-mcp daemon to overwrite arbitrary writable files owned by the victim user by exploiting symbolic link following. This results in integrity loss (truncation of files) and partial availability impact (potential disruption of victim processes relying on those files). There is no confidentiality impact reported. The CVSS v3.1 base score is 6.1 (medium severity), reflecting local attack vector with low complexity and no user interaction required.

A fix is available in chrome-devtools-mcp version 1.1.0. Users should upgrade to version 1.1.0 or later to remediate this vulnerability. Until upgrading, avoid running the daemon in environments where untrusted local users have write access to /tmp or the runtime directory. Patch status is not explicitly stated in vendor advisory content but the description confirms the issue is fixed in 1.1.0.