CVE-2026-53869 affects Hermes Agent prior to version 0.16.0. The vulnerability arises from missing authentication and validation on WebSocket upgrade requests at specific API endpoints. FastAPI middleware responsible for Host and Origin validation is not executed for these WebSocket connections, enabling DNS rebinding attacks. This allows remote attackers to bypass security controls and potentially execute arbitrary commands or access terminal output remotely without privileges or user interaction. The CVSS 4.0 score is 8.7, indicating high severity.

Remote attackers can exploit this vulnerability to bypass Host and Origin validation on WebSocket endpoints, leading to unauthorized command injection or terminal output disclosure. This compromises the confidentiality and integrity of the affected system. No known exploits are reported in the wild yet.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict access to the affected WebSocket endpoints and monitor for suspicious activity. Avoid exposing Hermes Agent instances to untrusted networks.