{"cve":"CVE-2021-3128","nvd":{"published":"2021-04-12T19:15:14.830","modified":"2026-06-17T04:04:42.857","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-834"],"references":["https://www.asus.com/Networking-IoT-Servers/Whole-Home-Mesh-WiFi-System/ZenWiFi-WiFi-Systems/ASUS-ZenWiFi-AX-XT8-/HelpDesk_BIOS/","https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX3000/HelpDesk_BIOS/","https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX55/HelpDesk_BIOS/","https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX56U/HelpDesk_BIOS/","https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX58U/HelpDesk_BIOS/"],"products":["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-ac66u_b1_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","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:zenwifi_ax_\\(xt8\\)_firmware"],"source":"nvd","synced_at":"2026-10-19T21:17:01.373894544+00:00"},"epss":{"cve":"CVE-2021-3128","score":0.02184,"percentile":0.82385,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}