This indicates an attack attempt to exploit a security bypass and cross-site request forgery vulnerability in the Huawei HG510 interface.
The vulnerability is a combination of a lack of cross-site forgery protection and a lack of validation when accessing rebootinfo.cgi. As a result, an attacker can inject a crafted uri and cause a Denial of Service to a valid user.
System Compromise: Remote attackers can gain control of vulnerable systems
Refer to the vendor's website for suggested workaround.