CVE-2021-45991
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 · uneditedTenda routers G1 and G3 v15.11.0.17(9502)_CN were discovered to contain a stack overflow in the function formAddVpnUsers. This vulnerability allows attackers to cause a Denial of Service (DoS) via the vpnUsers parameter.
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 overflow vulnerability in Tenda G1 and G3 routers (firmware v15.11.0.17) in the formAddVpnUsers function. The vpnUsers parameter lacks proper bounds checking, allowing attackers to overflow the stack and cause denial of service.
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= 15.11.0.17\(9502\)_cn= 15.11.0.17\(9502\)_cnCVSS 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 the Tenda router modelLocate the router device physically or access the admin interface to confirm the model is G1 or G3. This is typically found on a sticker on the device or in the web UI header.Affected if The device is NOT a Tenda G1 or G3 router.
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Determine the firmware versionLog into the router web interface (usually at 192.168.0.1), navigate to System Settings or Administration > Firmware Upgrade, and record the exact firmware version displayed.Affected if The firmware version is NOT 15.11.0.17(9502)_cn exactly.
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Verify VPN user management is accessibleCheck if the router has VPN functionality enabled and if the VPN user management page (formAddVpnUsers) is reachable. This is typically under VPN settings or User Management in the web interface.Affected if VPN feature is not enabled or the management interface is not accessible.
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Confirm the vpnUsers parameter is exposedIf you have access to the router's HTTP interface, attempt to access the VPN user addition form or inspect the web requests for a parameter named vpnUsers.Affected if The vpnUsers parameter is not present in the router's VPN management interface.
You are affected only if you have a Tenda G1 or G3 router with firmware version exactly 15.11.0.17(9502)_cn AND the VPN user management feature with the vpnUsers parameter is exposed and accessible.
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 dataUpdate to patched firmware if available; otherwise disable VPN user management from untrusted networks and implement network segmentation to limit exposure.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-45991 — 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-2021-45991 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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