Executive brief
Paperclip is a development framework that allows developers to build AI agents locally. By default, it runs in a trusted mode that automatically grants full administrative access to requests from localhost. An attacker can exploit DNS rebinding—a technique where a domain name resolves to both an attacker's server and the victim's local machine—to trick a developer's browser into making authenticated requests to their local Paperclip instance. This allows the attacker to execute arbitrary commands on the developer's computer, potentially stealing source code, credentials, SSH keys, and installing backdoors, all without the developer's knowledge or interaction beyond visiting a malicious webpage.
Technical details
The vulnerability is a missing Host header validation (CWE-862) in Paperclip's local_trusted deployment mode. Three factors combine: (1) local_trusted mode auto-authenticates all requests as instance admin with no checks; (2) Host header validation is disabled in local_trusted mode, only active in authenticated+private mode; (3) the process adapter executes arbitrary commands via spawn() without sandboxing. An attacker registers a domain with two DNS A records—one pointing to their server, one to 127.0.0.1 (localhost)—and crafts a malicious webpage. When a victim visits it, the browser connects to the attacker's server, which serves JavaScript that then makes API calls. As the server shuts down, the browser falls back to the 127.0.0.1 address, hitting the local Paperclip instance. Since Host header validation is missing, Paperclip accepts the request, auto-grants admin access, and the JavaScript creates a company with a process adapter configured to execute arbitrary bash commands. The attack requires only that a developer visit the malicious page; no credentials, clicks, or additional interaction are needed. No patch is currently available beyond upgrading to 0.3.1 or later.
Affected products
- Paperclip Paperclip before 0.3.1
Timeline
- 2026-07-22: disclosed: GitHub security advisory GHSA-x8hx-rhr2-9rf7 published
- 2026-08-21: advisory: CVE-2026-77087 published on NVD