CVE-2021-3128
HIGH
7.5
CVSS Score
Published: April 12, 2021 at 05:41 PM UTC
Updated: June 17, 2026 at 04:04 AM UTC
50 products affected across 1 vendorRT-AC86URT-AC68URT-AX88U
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Severity
HIGH7.5
Exploit prediction
EPSS 2%
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.
Affected
Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac1750-b1 (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac1900 (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac1900p (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac1900u (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac2900 (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac3100 (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac5300 (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac58u (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
asus-rt-ac65u (same device)
v < 3.0.0.4.386.42095v < 9.0.0.4.386.41994
Affected range stops below 3.0.0.4.386.42095, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.0.0.4.386.41994, so it looks safe — our inference, not a vendor statement
Remediation
No guide yetNo remediation guidance has been written for this CVE yet. What the record does show:
Patch and advisory 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/
References (27)
x_refsource_MISCProductVendor Advisory
Source: [email protected]
https://www.asus.com/Networking-IoT-Servers/Whole-Home-Mesh-WiFi-System/ZenWiFi-WiFi-Systems/ASUS-ZenWiFi-AX-XT8-/HelpDesk_BIOS/x_refsource_MISCProductVendor Advisory
Source: [email protected]
https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX3000/HelpDesk_BIOS/x_refsource_MISCProductVendor Advisory
Source: [email protected]
https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX55/HelpDesk_BIOS/x_refsource_MISCProductVendor Advisory
Source: [email protected]
https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX56U/HelpDesk_BIOS/x_refsource_MISCProductVendor Advisory
Source: [email protected]
https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX58U/HelpDesk_BIOS/x_refsource_MISCProductVendor Advisory
Source: [email protected]
https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX68U/HelpDesk_BIOS/x_refsource_MISCProductVendor Advisory
Source: [email protected]
https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX82U/HelpDesk_BIOS/x_refsource_MISCProductVendor Advisory
Source: [email protected]
https://www.asus.com/Networking-IoT-Servers/WiFi-6/All-series/RT-AX86U/HelpDesk_BIOS/CVSS
- Attack Vector
- NETWORK
- Complexity
- LOW
- Privileges
- NONE
- User Interaction
- NONE
- Scope
- UNCHANGED
- Confidentiality
- NONE
- Integrity
- NONE
- Availability
- HIGH
Vector?
Quick Info
StatusMODIFIED
CWE
CWE-834
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