This indicates an attack attempt to exploit a Security Bypass vulnerability in MusicCenter or Trivum Multiroom Setup Tool.
The vulnerability is due to an error when the vulnerable software attempts to improperly handle a craft HTTP request. An attacker can exploit this to bypass security of the target system by sending a craft HTTP request.
MusicCenter / Trivum Multiroom Setup Tool V8.76 - SNR 8604.26 - C4 Professional
Touchpad / Trivum WebTouch Setup V9 V2.53 build 13163
Security Bypass: Remote attackers can bypass security mechanism on vulnerable systems
Currently we are unaware of any vendor supplied patch or update available for this issue.