Description

Paperclip before 0.3.1 in default local_trusted mode fails to validate Host headers, allowing attackers to execute arbitrary commands via DNS rebinding. An attacker can craft a malicious webpage that, when visited by a developer running Paperclip locally, uses DNS rebinding to make authenticated API requests and execute commands through the process adapter.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.6",
  "pubDate": "2026-08-21T15:16:47.290Z",
  "pubdate": "2026-08-21T15:16:47.290Z",
  "executiveSummary": "Paperclip before 0.3.1 operating in default local_trusted mode suffers from a Host header validation vulnerability.\nThe vulnerability allows remote attackers to execute arbitrary commands through DNS rebinding attacks against local development instances.\nThe impacted product is Paperclip versions prior to 0.3.1.\nThe risk implication is severe, as successful exploitation leads to remote code execution on the host running the vulnerable service.\nAttacker capabilities include making authenticated API requests and executing arbitrary commands via the process adapter.\nExploitation requires a developer running Paperclip locally to visit a maliciously crafted webpage capable of executing a DNS rebinding attack.",
  "technicalDetails": "The root cause of the vulnerability is the absence of proper Host header validation in Paperclip prior to version 0.3.1 when running in the default local_trusted mode.\nThe vulnerable component is the HTTP request handling mechanism responsible for processing incoming connections and validating the Host header against trusted local origins.\nThe affected versions include all releases of Paperclip prior to 0.3.1 while utilizing the default local_trusted mode configuration.\nNetwork exposure is localized to developers running the service on their local machines, which typically bind to loopback interfaces.\nAuthentication and privilege requirements are bypassed because the attack leverages the implicit trust granted to local connections within the local_trusted mode, allowing the malicious web page to interact with the API as a trusted client.\nThe attack flow begins when an attacker crafts a malicious webpage containing JavaScript designed to initiate a DNS rebinding sequence against the target domain resolving to the local IP address.\nOnce the DNS rebinding successfully switches the IP address resolution from the attacker-controlled external server to the local loopback address (e.g., 127.0.0.1), the victim's browser sends standard HTTP requests to the locally running Paperclip instance.\nBecause Paperclip fails to validate the Host header, it treats these externally triggered requests as legitimate local traffic.\nThe malicious webpage leverages this trust to issue authenticated API requests directly to the local Paperclip service.\nPost-exploitation impact involves the attacker utilizing the process adapter functionality exposed via the API to execute arbitrary operating system commands in the context of the user running the Paperclip process."
}