The V8 inspector intentionally allows arbitrary code execution within the Workers sandbox for debugging. wrangler dev would previously start an inspector server listening on all network interfaces. This would allow an attacker on the local network to connect to the inspector and run arbitrary code. Additionally, the inspector server does not validate Origin/Host headers, granting an attacker that can trick any user on the local network into opening a malicious …
Sending specially crafted HTTP requests and inspector messages to Wrangler's dev server could result in any file on the user's computer being accessible over the local network. An attacker that could trick any user on the local network into opening a malicious website could also read any file.
The Wrangler command line tool (<=wrangler@3.1.0) was affected by a directory traversal vulnerability when running a local development server for Pages (wrangler pages dev command). This vulnerability enabled an attacker in the same network as the victim to connect to the local development server and access the victim's files present outside of the directory for the development server.