Paperclip before version 0.3.1 in its default local_trusted mode does not validate Host headers of incoming requests. An attacker can use DNS rebinding to redirect a developer's browser to the local instance, allowing authenticated API calls that trigger arbitrary commands through the process adapter. The flaw therefore permits an attacker to gain full code execution on the machine where Paperclip is running, compromising confidentiality, integrity, and availability of all data, configuration, and the host system.

The vulnerability affects the paperclipai Paperclip application before version 0.3.1. Developers running the 0.3.0 or earlier releases with the default local_trusted mode are at risk.

The CVSS score of 9.4 indicates critical severity. The EPSS score is not available, and the flaw is not listed in CISA KEV. The attack requires an attacker to host a malicious webpage and at the same time a developer to open that page while the local instance of Paperclip is running. DNS rebinding tricks the browser into making authenticated API requests to the local service, which then executes commands through the process adapter. Because the vulnerability only exists in local trusted mode, the attack surface is limited to developers who keep the local service running and visit arbitrary sites during development.