CVE-2021-35003
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 · uneditedThis vulnerability allows remote attackers to execute arbitrary code on affected installations of TP-Link Archer C90 1.0.6 Build 20200114 rel.73164(5553) routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of DNS responses. A crafted DNS message can trigger an overflow of a fixed-length, stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-14655.
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 · high confidenceStack-based buffer overflow in TP-Link Archer C90 routers (firmware 1.0.6) allows remote unauthenticated attackers to execute arbitrary code as root via crafted DNS response messages that overflow a fixed-length stack buffer.
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= 1.0.6CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 the router modelCheck the device label on the router or access the admin interface and look for the model number (usually at the top of the status page or in System Tools > Firmware Upgrade)Affected if The device is not a TP-Link Archer C90, then it is not affected by this specific CVE
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Check the firmware versionLog into the router admin interface (typically at 192.168.0.1), navigate to System Tools > Firmware Upgrade or Status page, and note the firmware version displayedAffected if The firmware version is exactly 1.0.6, then the device is affected by this vulnerability
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Verify DNS service exposureCheck if the router's DNS service is accessible from the WAN/internet by attempting to resolve DNS queries directed to the router's WAN IP address, or by reviewing the router's firewall settings under Advanced > Security > FirewallAffected if The DNS service is exposed to the WAN (internet-facing), then remote unauthenticated attackers can reach the vulnerable service
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Confirm DNS forwarding is enabledNavigate to Advanced > Network > DHCP Server (or similar DNS settings area) in the router admin interface and check if DNS forwarding is enabled, which is required for the vulnerable code path to be exercisedAffected if DNS forwarding/relay is enabled and the router processes DNS responses, then the vulnerable buffer overflow condition can be triggered
A TP-Link Archer C90 router running firmware version 1.0.6 with DNS service accessible from the WAN and DNS forwarding enabled is affected by this CVE and vulnerable to remote code execution.
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 dataApply TP-Link vendor firmware patch when available; until then, restrict WAN-facing access to router services and consider network segmentation to limit exposure.
- Consultation2.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-35003 — 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-2021-35003 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
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