An issue was discovered in Tenda W20E V4.0br_V15.11.0.6. Attackers may send overly long addDhcpRules data. When these rules enter the addDhcpRule function and are processed by ret = sscanf(pRule, " %d\t%[^\t]\t%[^\n\r\t]", &dhcpsIndex, dhcpsIP, dhcpsMac);, the lack of size validation for the rules could lead to buffer overflows in dhcpsIndex, dhcpsIP, and dhcpsMac.