CVE-2021-3128
HIGHCVSS 7.5/10EPSS 2.18%
Last modified
CVE-2021-3128 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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.. EPSS estimates a 2.18% chance of exploitation in the next 30 days.
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Asus | Zenwifi Ax \(Xt8\) Firmware | < 3.0.0.4.386.42095 |
| Asus | Zenwifi Ax \(Xt8\) Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ax3000 Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ax3000 Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ax55 Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ax55 Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ax56u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ax56u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ax58u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ax58u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ax68u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ax68u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ax82u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ax82u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ax86u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ax86u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ax88u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ax88u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac66u B1 Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac66u B1 Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac1750 B1 Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac1750 B1 Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac1900 Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac1900 Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac1900p Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac1900p Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac1900u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac1900u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac2900 Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac2900 Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac3100 Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac3100 Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac5300 Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac5300 Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac58u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac58u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac65u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac65u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac68p Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac68p Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac68r Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac68r Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac68rw Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac68rw Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac68u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac68u Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac68w Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac68w Firmware | < 9.0.0.4.386.41994 |
| Asus | Rt-Ac85u Firmware | < 3.0.0.4.386.42095 |
| Asus | Rt-Ac85u Firmware | < 9.0.0.4.386.41994 |
Showing 50 of 54 affected configurations. See NVD for the full list.
References
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX3000/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX55/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX56U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX58U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX68U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX82U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX86U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX88U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC1750_B1/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC1900/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC1900P/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC1900U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC2900/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC3100/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC5300/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC58U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC65U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68P/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68R/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68RW/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68W/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC85U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC86U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC88U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX3000/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX55/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX56U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX58U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX68U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX82U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX86U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX88U/HelpDesk_BIOS/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC1750_B1/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC1900/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC1900P/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC1900U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC2900/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC3100/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC5300/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC58U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC65U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68P/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68R/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68RW/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC68W/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC85U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC86U/HelpDesk_download/Product, Vendor Advisory
- https://www.asus.com/supportonly/RT-AC88U/HelpDesk_download/Product, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is 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 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.
How severe is CVE-2021-3128?
CVE-2021-3128 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 2.18% probability of exploitation in the next 30 days.
How do I fix CVE-2021-3128?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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