CVE-2021-3128 in the critical feed json
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 i…
published 2021-04-12 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26477
- cvss
- 7.5
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 16.2%
- EPSS 16.2% chance of exploitation in 30 days, percentile 96%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- asus zenwifi_ax_(xt8)_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ax3000_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ax55_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ax56u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ax58u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ax68u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ax82u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ax86u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ax88u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac66u_b1_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac1750_b1_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac1900_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac1900p_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac1900u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac2900_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac3100_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac5300_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac58u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac65u_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
- asus rt-ac68p_firmware 3.0.0.4.386.42095, 9.0.0.4.386.41994
Exploit prediction
16.19% chance of exploitation in the next 30 days, higher than 96% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVD | 2.0 | 5.0 | AV:N/AC:L/Au:N/C:N/I:N/A:P |
Classification
- Weakness
-
- CWE-834 Excessive Iteration
References
-
asus.com
/Networking-IoT-Servers/WiFi-6/All-series/RT-AX3000/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/Whole-Home-Mesh-WiFi-System/ZenWiFi-WiFi-Systems/ASUS-ZenWiFi-AX-XT8-/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/WiFi-6/All-series/RT-AX88U/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/WiFi-6/All-series/RT-AX86U/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/WiFi-6/All-series/RT-AX82U/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/WiFi-6/All-series/RT-AX68U/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/WiFi-6/All-series/RT-AX58U/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/WiFi-6/All-series/RT-AX56U/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/WiFi-6/All-series/RT-AX55/HelpDesk_BIOS/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC5300/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC88U/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC3100/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC86U/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC2900/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC1750_B1/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC1900/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC1900P/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC1900U/HelpDesk_download/
product, vendor-advisory
-
asus.com
/Networking-IoT-Servers/WiFi-Routers/ASUS-WiFi-Routers/RT-AC66U-B1/HelpDesk_Download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC68P/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC68R/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC68RW/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC68U/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC58U/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC85U/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC65U/HelpDesk_download/
product, vendor-advisory
-
asus.com
/supportonly/RT-AC68W/HelpDesk_download/
product, vendor-advisory
Sources
- CVE List CVE-2021-3128
- NVD CVE-2021-3128
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.