Horde Virtual File System (VFS) API before 3.0.1 contains an OS command injection vulnerability in the Horde_Vfs_Smb driver where the _escapeShellCommand() method fails to sanitize command substitution sequences, allowing authenticated attackers to inject arbitrary shell commands through user-controlled filenames. Attackers can supply malicious filenames containing unescaped command substitution payloads through operations such as file upload, folder creation, rename, or deletion, which are interpolated into a double-quoted shell context and executed via proc_open() through /bin/sh -c before smbclient runs, resulting in arbitrary command execution on the underlying system.