Completed another Hack The Box machine: Reactor, an Easy-difficulty Linux challenge.

The initial foothold came from enumerating the Next.js application running on port 3000. Version fingerprinting identified a vulnerable React canary release associated with CVE-2025-55182 (React2Shell). Further testing confirmed remote code execution through the React Server Components functionality, providing access as the node user.

From the application environment, the SQLite database exposed credentials for the engineer account. After recovering the password from the stored MD5 hash, SSH access provided the user-level foothold.

For privilege escalation, process enumeration revealed a root-owned Node.js service with the inspector exposed on localhost. The Node inspector provided a path to execute code within the root process and modify /bin/bash permissions, ultimately leading to a root shell.

I also explored an alternative approach using SSH local port forwarding and Chrome DevTools to access the remote Node inspector.

Another useful HTB machine for practicing web enumeration, version fingerprinting, application-layer exploitation, Linux enumeration, and Node.js debugging interfaces.

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