# CVE-2021-3125: Denial of service in n/a

> Attackers can cause excessive network traffic and routing loops in TP-Link routers using IPv6, leading to denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Apr 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-w422-w3vf-f63f

## What is CVE-2021-3125?

CVE-2021-3125 is a high-severity denial of service vulnerability in n/a, published on 12 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In TP-Link TL-XDR3230 < 1.0.12, TL-XDR1850 < 1.0.9, TL-XDR1860 < 1.0.14, TL-XDR3250 < 1.0.2, TL-XDR6060 Turbo < 1.1.8, TL-XDR5430 < 1.0.11, and possibly others, 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.

Weakness: CWE-834 (Excessive Iteration)

## Which versions are affected by CVE-2021-3125?

It affects 6 products.


Products: Tp-Link Tl-Xdr1850 Firmware, Tp-Link Tl-Xdr1860 Firmware, Tp-Link Tl-Xdr3230 Firmware, Tp-Link Tl-Xdr3250 Firmware, Tp-Link Tl-Xdr5430 Firmware, Tp-Link Tl-Xdr6060 Firmware.

## How do I fix CVE-2021-3125?

No fix has been published for CVE-2021-3125 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-3125 being exploited?

There is no known exploitation of CVE-2021-3125 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3125 and fix it if it is affected.

What it is: CVE-2021-3125 is a high-severity denial of service vulnerability in n/a, published on 12 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3125 in the wild and no public exploit code.

Affected product: n/a. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-3125/ (Markdown: https://insights.sbomify.com/CVE-2021-3125/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3125
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3125
- OSV: https://osv.dev/vulnerability/CVE-2021-3125

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3125/
Summaries are generated and may contain mistakes; the official description above is the record.