CVE-2021-34947
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 · uneditedNETGEAR R7800 net-cgi Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R7800 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the parsing of the soap_block_table file. The issue results from the lack of proper validation of user-supplied data, which can result in a write past the end of an allocated data structure. An attacker can leverage this vulnerability to execute code in the context of root. . Was ZDI-CAN-13055.
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 confidenceThe vulnerability exists in the net-cgi component of NETGEAR R7800 routers. During parsing of the soap_block_table file, the application fails to properly validate user-supplied data, leading to an out-of-bounds write past the end of an allocated data structure. This allows network-adjacent attackers to achieve root-level code execution without authentication.
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< 1.0.1.64< 1.0.1.66< 1.0.1.106< 1.0.1.106< 1.0.1.86< 1.0.0.146< 1.0.2.164< 1.0.0.146CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:A/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 router modelAccess the router web interface or check the device label to confirm the exact model number (e.g., D7800, Ex2700, Ex6100, Ex6150, Ex6200, Ex6250, Ex6400, Ex6400v2)Affected if The model is one of the affected devices listed in the CVE
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Check installed firmware versionLog into the router web interface and navigate to the Administration or Firmware Update section to view the current firmware version, or use the router's API if availableAffected if The firmware version is lower than the threshold for your model: D7800 < 1.0.1.64, Ex2700 < 1.0.1.66, Ex6100/Ex6150 < 1.0.1.106, Ex6200 < 1.0.1.86, Ex6250/Ex6400v2 < 1.0.0.146, Ex6400 < 1.0.2.164
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Verify net-cgi component is accessibleAttempt to access the net-cgi binary or endpoints on the router (typically at /cgi-bin/ or similar web paths). Use a web request to the router's IP on common HTTP/HTTPS portsAffected if The net-cgi component responds to requests from the network, indicating it is exposed
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Confirm soap_block_table file existsIf you have SSH or telnet access to the router, check for the presence of the soap_block_table file in the web server's configuration or data directoriesAffected if The soap_block_table file exists and is accessible for parsing by the net-cgi component
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Check remote management exposureReview the router's administration settings to determine if remote management (Web GUI access from WAN) is enabled. Check firewall rules and port forwarding settingsAffected if Remote administration is enabled, allowing network-adjacent attackers to reach the vulnerable net-cgi component
You are affected if your router model matches one of the listed products AND your firmware version is below the specified threshold AND the net-cgi component is network-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.
dbcve · scoped1.0.0.1461.0.1.641.0.1.66
Apply the vendor-supplied firmware patch from NETGEAR. If unavailable, restrict network access to the router's management interface and disable remote administration features to reduce attack surface.
Device-specific firmware: D7800 to 1.0.1.64+, Ex2700 to 1.0.1.66+, Ex6100/Ex6150 to 1.0.1.106+, Ex6200 to 1.0.1.86+, Ex6250/Ex6400v2 to 1.0.0.146+, Ex6400 to 1.0.2.164+
- Identify the exact NETGEAR device model from the affected list (D7800, Ex2700, Ex6100, Ex6150, Ex6200, Ex6250, Ex6400, or Ex6400v2)
- Navigate to NETGEAR's support website (support.netgear.com) or the specific product download page
- Download the firmware version equal to or higher than the fixed version for your device: D7800: 1.0.1.64, Ex2700: 1.0.1.66, Ex6100: 1.0.1.106, Ex6150: 1.0.1.106, Ex6200: 1.0.1.86, Ex6250: 1.0.0.146, Ex6400: 1.0.2.164, Ex6400v2: 1.0.0.146
- Access the router/extender's web management interface
- Locate the Firmware Update or Administration section
- Upload and apply the new firmware file
- Verify the firmware version after update confirms the patch was applied
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-34947 — 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-2021-34947 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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