{"id":"CVE-2021-3128","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-3128","generatedAt":"2026-10-27T21:19:56.653Z","title":"In ASUS RT-AX3000, ZenWiFi AX (XT8), RT-AX88U, and other ASUS routers with firmware < 3.0.0.4.386.42095 or < 9.0.0.4.386.41994, when IPv6 is used, a routing loop can occur that generates excessive network traffic between an affected device and its…","description":"In ASUS RT-AX3000, ZenWiFi AX (XT8), RT-AX88U, and other ASUS routers with firmware < 3.0.0.4.386.42095 or < 9.0.0.4.386.41994, when IPv6 is used, a routing loop can occur that generates excessive network traffic between an affected device and its upstream ISP's router. This occurs when a link prefix route points to a point-to-point link, a destination IPv6 address belongs to the prefix and is not a local IPv6 address, and a router advertisement is received with at least one global unique IPv6 prefix for which the on-link flag is set.","published":"2021-04-12T19:15:15.000Z","lastModified":"2026-06-17T04:04:43.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-834"],"affected":["asus/zenwifi ax \\(xt8\\) firmware","asus/rt-ax3000 firmware","asus/rt-ax55 firmware","asus/rt-ax56u firmware","asus/rt-ax58u firmware","asus/rt-ax68u firmware","asus/rt-ax82u firmware","asus/rt-ax86u firmware","asus/rt-ax88u firmware","asus/rt-ac66u b1 firmware","asus/rt-ac1750 b1 firmware","asus/rt-ac1900 firmware","asus/rt-ac1900p firmware","asus/rt-ac1900u firmware","asus/rt-ac2900 firmware","asus/rt-ac3100 firmware","asus/rt-ac5300 firmware","asus/rt-ac58u firmware","asus/rt-ac65u firmware","asus/rt-ac68p firmware","asus/rt-ac68r firmware","asus/rt-ac68rw firmware","asus/rt-ac68u firmware","asus/rt-ac68w firmware","asus/rt-ac85u firmware","asus/rt-ac86u firmware","asus/rt-ac88u firmware"],"epss":{"score":0.02184,"percentile":0.8226,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (2.18%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://www.asus.com/Networking-IoT-Servers/Whole-Home-Mesh-WiFi-System/ZenWiFi-WiFi-Systems/ASUS-ZenWiFi-AX-XT8-/HelpDesk_BIOS/","tags":["Product","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX3000/HelpDesk_BIOS/","tags":["Product","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX55/HelpDesk_BIOS/","tags":["Product","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX56U/HelpDesk_BIOS/","tags":["Product","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX58U/HelpDesk_BIOS/","tags":["Product","Vendor 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