CVE-2026-6240
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 DeleteUsers service, due to insufficient boundary checks when handling multiple user deletion parameters. An authenticated attacker can send a crafted malicious request containing an excessive number of identifiers to overflow stack memory. Successful exploitation may result in a service crash or deadlock, leading to DoS affecting device management and monitoring functionality.
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 Tapo C520WS v2 ONVIF DeleteUsers service due to insufficient boundary checks when processing multiple user deletion parameters. An authenticated attacker can overflow stack memory by sending a crafted request with excessive identifiers, causing service crash or deadlock.
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 the device modelCheck the device label, web interface, or administrative console for the exact model number (Tapo C520WS v2).Affected if The device is a Tapo C520WS v2 unit.
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Determine the installed firmware versionAccess the device admin interface (usually via web browser at the device IP) and navigate to the Firmware or Device Info section to view the current firmware version.Affected if The firmware version is the v2 release for Tapo C520WS (compare to any available patched version from vendor).
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Verify ONVIF service is enabledCheck the device settings under Network or Advanced settings for ONVIF configuration. Use an ONVIF device manager tool to probe the device on port 2020 or 8080 if accessible.Affected if ONVIF service is enabled and accessible on the network.
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Confirm ONVIF authentication is configuredReview ONVIF security settings to determine if authentication is required for ONVIF service access. Check if default credentials are in use or if a custom ONVIF user account exists.Affected if ONVIF service allows authenticated access (valid ONVIF credentials exist or can be created).
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Assess network exposure of ONVIF serviceReview firewall rules, router port forwarding, or network segmentation to determine if ONVIF ports are exposed to untrusted networks.Affected if ONVIF service is reachable from networks beyond trusted administration IPs.
If the device is a Tapo C520WS v2 with ONVIF enabled and accessible to an authenticated attacker, the environment is affected by this vulnerability.
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; in interim, restrict network access to the ONVIF service to authenticated, trusted users only and implement network segmentation to limit exposure.
- Consultation8.0 h
- Implementation16.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $10,240.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-6240 — 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-2026-6240 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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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