CVE-2021-35394
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 a diagnostic tool called 'MP Daemon' that is usually compiled as 'UDPServer' binary. The binary is affected by multiple memory corruption vulnerabilities and an arbitrary command injection vulnerability that can be exploited by remote unauthenticated attackers.
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 a vulnerable MP Daemon diagnostic tool (compiled as UDPServer binary) affected by multiple memory corruption vulnerabilities and an arbitrary command injection flaw, exploitable by remote unauthenticated attackers due to insufficient input validation in the UDP 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>= 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 Realtek Jungle SDK devices on your networkScan your network for devices using Realtek RTL819x WiFi chipsets. Review device inventory or use network scanning to identify hardware vendors and model numbers known to use Realtek chipsets (common in routers, access points, and IoT devices).Affected if Devices with Realtek RTL819x chipsets are found in your environment
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Locate firmware version informationAccess the device management interface, command line, or review firmware image metadata to determine the SDK version. For each device, look for version strings containing 'Jungle SDK', 'RTL819x', or similar Realtek SDK identifiers.Affected if The device firmware is based on Realtek Jungle SDK and version falls between 2.0 and 3.4.14b inclusive
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Identify if MP Daemon (UDPServer) is presentExamine the firmware image or running system for the presence of a binary named 'UDPServer', 'MP Daemon', or similar diagnostic service. Check device startup scripts or process list for these services.Affected if The MP Daemon or UDPServer diagnostic tool is present in the firmware or running on the device
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Verify UDP service is exposedPerform a UDP port scan against the device from an external interface. Check if any UDP service listening for diagnostic packets is accessible from untrusted networks. Review firewall rules and network accessibility of the device.Affected if The UDP diagnostic service is reachable from network segments where untrusted users can send packets
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Confirm SDK version is within affected rangeCompare the identified SDK or firmware version against the vulnerable range: versions >= 2.0 and <= 3.4.14b. If version cannot be determined but SDK is present, treat as potentially affected.Affected if The identified version is >= 2.0 and <= 3.4.14b, or version cannot be determined but Realtek Jungle SDK is confirmed
Your environment is affected if you have devices running firmware based on Realtek Jungle SDK versions 2.0 through 3.4.14b with the MP Daemon/UDPServer diagnostic service enabled and accessible on the network.
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 · scopedIdentify all devices and products using the Realtek Jungle SDK and apply vendor-supplied firmware updates; if updates are unavailable, disable the MP Daemon/UDPServer service or implement network segmentation to block unauthorized UDP access to the service.
Contact Realtek for the patched Rtl819x Jungle SDK version (beyond v3.4.14b)
- Contact Realtek directly to obtain the patched version of the Rtl819x Jungle SDK that addresses CVE-2021-35394
- Request the specific patch or updated SDK version from Realtek's security team
- Apply the vendor-provided patch following their official remediation guidance
- Verify the patch has been applied by checking the UDPServer/MP Daemon binary version
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation4.0 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-2021-35394 — 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-2021-35394 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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