Dann könnte man mit String.Split arbeiten.
msg.payload = msg.payload.split(";")[1];
return msg;
Hier mal ein kleines "Test-Node":

[{"id":"91ca6ce1.f6872","type":"inject","z":"eeacac8e.84e57","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"hex02;25454585754525421545;hex03","payloadType":"str","x":150,"y":400,"wires":[["795a8ecf.b1929"]]},{"id":"955a20b4.09c3c","type":"debug","z":"eeacac8e.84e57","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":450,"y":400,"wires":[]},{"id":"795a8ecf.b1929","type":"function","z":"eeacac8e.84e57","name":"","func":"msg.payload = msg.payload.split(\";\")[1];\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":300,"y":400,"wires":[["955a20b4.09c3c"]]}]