CVE-2021-3125
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceA routing loop vulnerability in TP-Link TL-XDR series routers (models and versions specified) causes excessive network traffic when IPv6 is used. The loop occurs when a link prefix route points to a point-to-point link, a destination IPv6 address belongs to the prefix and is not local, and a router advertisement with a global unique IPv6 prefix has the on-link flag set.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 1.0.12< 1.0.11< 1.0.2< 1.0.14< 1.0.9< 1.1.8CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify router modelAccess router admin panel (typically at 192.168.0.1 or 192.168.1.1) and check the device model name in System or Status settings. Look for TL-XDR3230, TL-XDR5430, TL-XDR3250, TL-XDR1860, TL-XDR1850, or TL-XDR6060.Affected if Router is any TL-XDR series model listed in the affected products
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Check firmware versionIn router admin panel, go to System or Firmware settings and note the installed firmware version number.Affected if Firmware version is below 1.0.12 for XDR3230, below 1.0.11 for XDR5430, below 1.0.2 for XDR3250, below 1.0.14 for XDR1860, below 1.0.9 for XDR1850, or below 1.1.8 for XDR6060
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Verify IPv6 is enabledIn router admin panel, navigate to IPv6 or Network settings and confirm whether IPv6 is turned on.Affected if IPv6 is enabled on the router (the vulnerability only triggers when IPv6 traffic is in use)
User is affected if they have a TL-XDR series router with a vulnerable firmware version listed above AND IPv6 is enabled on their network.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data1.0.21.0.91.0.11
Update router firmware to versions beyond those listed as vulnerable (TL-XDR3230 to 1.0.12+, TL-XDR1850 to 1.0.9+, TL-XDR1860 to 1.0.14+, TL-XDR3250 to 1.0.2+, TL-XDR6060 Turbo to 1.1.8+, TL-XDR5430 to 1.0.11+). As a workaround, disable IPv6 or filter router advertisements from upstream until firmware update is possible.
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-3125 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-3125 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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