CVE-2026-6239
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 · uneditedA stack‑based buffer overflow vulnerability exists in Tapo C520WS v2 in the ONVIF CreateUsers service, where the device fails to properly validate the number of XML user nodes during request processing. An authenticated attacker can send a specially crafted ONVIF request containing an excessive number of user entries to trigger memory corruption. Successful exploitation may cause the ONVIF management service to terminate unexpectedly, resulting in a denial‑of‑service (DoS) condition that disrupts device configuration and management functions.
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 confidenceA stack-based buffer overflow in the ONVIF CreateUsers service of Tapo C520WS v2 allows an authenticated attacker to send specially crafted ONVIF requests containing an excessive number of XML user nodes. The device fails to validate the count of user entries before copying them into a fixed-size stack buffer, causing memory corruption that crashes the ONVIF management service.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- Adjacent
- Complexity
- Low
- Privileges
- High
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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 device modelAccess the device web interface or check the device label to confirm the exact model is Tapo C520WS v2Affected if Device is not a Tapo C520WS v2 model, then not affected by this specific CVE
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Verify ONVIF service is enabledCheck the device settings web interface under Network or Services settings for ONVIF configuration, or scan the device network ports (typically 80, 8080, or ONVIF-specific ports) to see if ONVIF endpoints respondAffected if ONVIF service is disabled or not accessible, then the attack surface does not exist
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Confirm ONVIF authentication is in useAttempt to access the ONVIF service wsdl or device information service without credentials, or review ONVIF user configuration in the device management interfaceAffected if ONVIF service allows anonymous access or has weak/default credentials, indicating higher exposure but authenticated attacker is required for this specific flaw
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Check firmware versionAccess device settings, typically under System or About section, to locate the firmware version stringAffected if Firmware is older than the version that includes the vendor fix (compare against any available release notes from TP-Link)
A user is affected if they have a Tapo C520WS v2 with ONVIF service enabled and accessible, where an attacker could authenticate to the ONVIF interface and send crafted CreateUsers requests with excessive XML user nodes.
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 vendor firmware updates when available; until then, restrict network access to the ONVIF service to trusted IP addresses and monitor for service disruptions.
- Consultation4.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,152.
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Free · runs locallyCheck whether your project pulls in CVE-2026-6239 — 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-2026-6239 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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- Version or environment caveats, and links to real fixes
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