CVE-2021-3128
HIGHEPSS 81th pctlDescription
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 to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Elevated risk: more likely to be exploited than 81% of all known CVEs.
References
Related Vulnerabilities
Other CWE-834 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2021-35515 | High | 7.5 | 12% | - | Fix |
| CVE-2021-39924 | High | 7.5 | 4.9% | - | Fix |
| CVE-2023-1993 | Medium | 6.3 | 4.1% | - | Fix |
| CVE-2018-14342 | High | 7.5 | 3.7% | - | Fix |
| CVE-2020-14303 | High | 7.5 | 3.5% | - | Fix |
| CVE-2018-9133 | Medium | 6.5 | 3.2% | - | Fix |
Common questions
How do I fix CVE-2021-3128?
Published advisories record a fix for 27 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2021-3128 being actively exploited?
Not that we know of. CVE-2021-3128 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 2.2% is the estimated probability that it will be exploited in the next 30 days. That is higher than 81% of all scored CVEs.
How severe is CVE-2021-3128?
CVE-2021-3128 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-3128 affect?
Published advisories record a fix for rt-ac1750 b1 firmware (NVD), rt-ac1900 firmware (NVD), rt-ac1900p firmware (NVD), rt-ac1900u firmware (NVD), and 23 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.