Pheditor has an authenticated terminal command whitelist bypass

Summary

Pheditor 2.0.4 has an authenticated terminal command whitelist bypass.

The terminal feature checks whether the submitted command starts with one of the configured TERMINAL_COMMANDS values, then passes the full command string to shell_exec(). Shell command substitution such as $() is not blocked, so an authenticated user with the terminal permission can bypass a restricted command allowlist and execute arbitrary shell commands as the web server user.

Details

Tested repository:

https://github.com/pheditor/pheditor

Tested commit:

62b43df7cb8956a9b0deb9bec278ca8676c890c5

Affected version:

Pheditor 2.0.4

Relevant code in pheditor.php:

• The terminal handler receives $_POST['command'] and stores it in $command.
• It blocks only &, ;, and ||.
• It checks whether $command starts with one of the configured values in TERMINAL_COMMANDS.
• It then passes the full command string to shell_exec().

Relevant logic:

$command = $_POST['command'];

if (strpos($command, '&') !== false || strpos($command, ';') !== false || strpos($command, '||') !== false) {
    echo json_error("Illegal character(s) in command (& ; ||)\n");
    exit;
}

foreach ($terminal_commands as $value) {
    $value = trim($value);

    if (strlen($command) >= strlen($value) && substr($command, 0, strlen($value)) == $value) {
        $command_found = true;
        break;
    }
}

$output = shell_exec((empty($dir) ? null : 'cd ' . escapeshellarg($dir) . ' && ') . $command . ' && echo \ ; pwd');

Because the whitelist check is prefix-based and the full command is executed by a shell, a command such as ls$(...) passes when ls is allowed, while the command substitution is still executed by the shell.

PoC

This was reproduced locally with Docker and PHP 8.3.

For a strict test, the configured command allowlist was changed to only allow ls:

define('TERMINAL_COMMANDS', 'ls');

Control request:

command=whoami

Observed result: