Buddy if you see almost 50-60% routers in market are vulnerable because most of them are running very older version of linux underneath. For that older linux version there are plenty of vulnerabilities that can be exploited. Vendor don't bother to fix those vulnerabilities because they don't see any returns on that investment. Most of the normal consumer will not never know about those vulnerabilities ever so manufacturer never release patches
The affected device models include ZTE H108N and H108NV2.1; D-Link 2750E, 2730U and 2730E; Sitecom WLM-3600, WLR-6100 and WLR-4100; FiberHome HG110; Planet ADN-4101; Digisol DG-BG4011N; and Observa Telecom BHS_RTA_R1A.