The Node.js web service on VOS (previously Versa FlexVNF) is used for URL-based Zero Touch Provisioning (ZTP) of the VOS appliance and is not required after provisioning is complete. The /authenticate endpoint of this service passes user-supplied username and password values to child_process.exec() through a sanitizer (escapeRegExp) that removes regular expression metacharacters but not newline characters. An unauthenticated attacker can inject a newline character into the username field to execute arbitrary shell commands as the versa OS service user. No credentials are required; the attacker needs only a CSRF token, which can be obtained from an unauthenticated page load. 

Versa’s security hardening guide for Hubs, Branches, and Controllers recommends disabling the Node.js web service after the initial provisioning of the VOS device. This vulnerability is not exploitable on VOS devices where the Node.js web service has been disabled.