CVE-2021-35395
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 · uneditedRealtek Jungle SDK version v2.x up to v3.4.14B provides an HTTP web server exposing a management interface that can be used to configure the access point. Two versions of this management interface exists: one based on Go-Ahead named webs and another based on Boa named boa. Both of them are affected by these vulnerabilities. Specifically, these binaries are vulnerable to the following issues: - stack buffer overflow in formRebootCheck due to unsafe copy of submit-url parameter - stack buffer overflow in formWsc due to unsafe copy of submit-url parameter - stack buffer overflow in formWlanMultipleAP due to unsafe copy of submit-url parameter - stack buffer overflow in formWlSiteSurvey due to unsafe copy of ifname parameter - stack buffer overflow in formStaticDHCP due to unsafe copy of hostname parameter - stack buffer overflow in formWsc due to unsafe copy of 'peerPin' parameter - arbitrary command execution in formSysCmd via the sysCmd parameter - arbitrary command injection in formWsc via the 'peerPin' parameter Exploitability of identified issues will differ based on what the end vendor/manufacturer did with the Realtek SDK webserver. Some vendors use it as-is, others add their own authentication implementation, some kept all the features from the server, some remove some of them, some inserted their own set of features. However, given that Realtek SDK implementation is full of insecure calls and that developers tends to re-use those examples in their custom code, any binary based on Realtek SDK webserver will probably contains its own set of issues on top of the Realtek ones (if kept). Successful exploitation of these issues allows remote attackers to gain arbitrary code execution on the device.
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 confidenceRealtek Jungle SDK versions v2.x through v3.4.14B contain multiple critical vulnerabilities in their HTTP web server management interface (both Go-Ahead 'webs' and Boa 'boa' variants). Six stack buffer overflows exist due to unsafe parameter copying in formRebootCheck, formWsc, formWlanMultipleAP, formWlSiteSurvey, formStaticDHCP, and formWsc (peerPin). Additionally, formSysCmd allows arbitrary command execution via sysCmd parameter, and formWsc allows command injection via peerPin. These allow remote unauthenticated attackers to achieve arbitrary code execution.
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>= 2.0, <= 3.4.14bCVSS 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 device firmware and SDK versionExtract firmware from the device or check device documentation for the Realtek Rtl819x Jungle SDK version. Look for version strings like 'RTL819X' or 'Jungle' in firmware binaries, boot logs, or system information.Affected if The installed SDK version falls within >= 2.0 and <= 3.4.14b
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Verify the HTTP web server is exposedScan the device for open HTTP ports (commonly 80, 443, 8080). Use 'nmap -sV <device-ip>' or check with 'curl -I http://<device-ip>' to confirm the web interface is accessible.Affected if The HTTP server is reachable on the network (especially from untrusted networks)
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Determine the web server variantInspect HTTP response headers or examine the web interface pages. Look for 'Server' header values containing 'GoAhead' or 'Boa', and check for the specific form handler URLs like /goform/formSysCmd, /goform/formWsc, /goform/formWlSiteSurvey.Affected if The web server is identified as Go-Ahead 'webs' or Boa variant from the Realtek SDK
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Test for vulnerable form handler accessibilitySend HTTP POST requests to the device targeting /goform/formSysCmd (with sysCmd parameter) or /goform/formWsc (with peerPin parameter). Example: 'curl -X POST -d "sysCmd=id" http://<device-ip>/goform/formSysCmd'Affected if The form handlers respond without authentication (401/403) or return command output, indicating they are accessible and potentially vulnerable
The device is likely affected if it runs Realtek Rtl819x Jungle SDK version 2.0 through 3.4.14b with the HTTP web server (Go-Ahead or Boa) exposed and the vulnerable form handlers are accessible without authentication.
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 dataOrganizations should identify all devices using Realtek Jungle SDK and apply vendor-supplied firmware updates. Where updates are unavailable, network segmentation and disabling WAN access to the management interface should be implemented as compensating controls.
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- Review / QA8.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-35395 — 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-2021-35395 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
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