An issue was discovered in the 3CX Phone System Management Console prior to version 18 Update 3 FINAL. An unauthenticated attacker could abuse improperly secured access to arbitrary files on the server leading to cleartext credential disclosure. Afterwards the authenticated attacker is able to upload a file that overwrites a 3CX service binary leading to Remote Code Execution as NT AUTHORITY\\SYSTEM on Windows installations. Versions prior to version 18 Hotfix 1 Build 18.0.3.461 March 2022 are prone to an additional unauthenticated file system access to C:\\Windows\\System32.