The vulnerability arises from incomplete remediation of a previous issue (CVE-2026-2577). Although the server binding was restricted to localhost and an optional token authentication was introduced, token authentication is disabled by default and the server does not validate the Origin header during the WebSocket handshake. Browsers do not enforce Same-Origin Policy on WebSockets unless the server explicitly denies cross-origin connections, allowing any website visited by the user to connect to ws://127.0.0.1:3001/ and fully control the bridge API. This can lead to session hijacking and unauthorized message access and sending. The vulnerability is resolved in nanobot version 0.1.5.

Successful exploitation allows an attacker to hijack the WhatsApp session managed by the nanobot bridge, read incoming messages, steal authentication QR codes, and send messages on behalf of the user. This compromises user privacy and account integrity. The CVSS score is 8.0 (high), reflecting network attack vector, high impact on confidentiality and integrity, and requiring user interaction with a malicious website.

This vulnerability is fixed in nanobot version 0.1.5. Users and administrators should upgrade to version 0.1.5 or later to remediate this issue. Since no official patch link or vendor advisory is provided, verify the upgrade from the official HKUDS nanobot release channels. Until upgraded, users should avoid visiting untrusted websites while running vulnerable versions of the bridge. Patch status is not explicitly confirmed by a vendor advisory but the description states the issue is fixed in 0.1.5.