Q: Is this a vulnerability?
A: Of course it is! (It is also necessary).
Q: Is this a vulnerability worth worrying about?
A: Probably not. It Dumping should be protected by an administration password and your physical security. (But those, you should worry about. I.e. set the admin password securely, and put the router in access controlled space.)
As others have pointed out, disposal runs a risk if you reuse the password. Depending on your security model, this may require incinerating the device.