CVE intelligence and bounded remediation

CVE-2021-3128 — Asus Zenwifi Ax (Xt8) Firmware security vulnerability

High CVSS 7.5

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.

Severity
High
CVSS
7.5 (3.1)
Published
2021-04-12
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-834

Affected products

  • asus / zenwifi_ax_(xt8)_firmware
  • asus / rt-ax3000_firmware
  • asus / rt-ax55_firmware
  • asus / rt-ax56u_firmware
  • asus / rt-ax58u_firmware
  • asus / rt-ax68u_firmware

Showing 6 representative product identities from 54 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Resource exhaustion and denial of service

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Identify attacker-influenced work factors including input size, nesting, compression, fan-out, regex cost, allocation, recursion, retries, and connection lifetime.
  • Map per-request and shared CPU, memory, disk, descriptor, thread, queue, and downstream-service limits.
  • Determine whether authentication, tenancy, quotas, and rate controls apply before expensive processing begins.

Remediate safely

  • Bound input size, nesting, expansion, work, concurrency, queue depth, retries, and execution time before resource-intensive processing.
  • Release resources on every success, error, cancellation, and timeout path and use backpressure instead of unbounded buffering.
  • Update affected components and add small deterministic tests that assert resource ceilings rather than exhausting a host.

Authoritative sources

Complete CVE record and remediation plan

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