CVE-2020-5131
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 · uneditedSonicWall NetExtender Windows client vulnerable to arbitrary file write vulnerability, this allows attacker to overwrite a DLL and execute code with the same privilege in the host operating system. This vulnerability impact SonicWall NetExtender Windows client version 9.0.815 and earlier.
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 SonicWall NetExtender Windows client versions 9.0.815 and earlier contains an arbitrary file write vulnerability that allows a local or network-attacker to overwrite a DLL file on the system. When the NetExtender client loads this malicious DLL, it executes with the same privileges as the client application, enabling 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<= 9.0.815CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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.
-
Confirm NetExtender is installedOpen Programs and Features (appwiz.cpl) or check for NetExtender in C:\Program Files\SonicWall\NetExtender or C:\Program Files (x86)\SonicWall\NetExtender. You can also run 'Get-Process netextender' in PowerShell if the client is active.Affected if NetExtender is present on the system with version 9.0.815 or lower
-
Identify installed NetExtender versionRight-click the NetExtender icon in the system tray and select 'About' or check the version in the Windows Programs and Features list. Alternatively, right-click the NeTextender.exe file in the installation folder and view Properties > Details.Affected if The displayed version is 9.0.815 or any version lower (for example, 9.0.800, 9.0.7xx, etc.)
-
Locate DLL loading directoriesCheck the NetExtender installation folder (typically C:\Program Files\SonicWall\NetExtender) and the Windows system directories it may reference. Use Sysinternals Process Monitor to observe DLL load behavior when NetExtender starts.Affected if NetExtender loads DLLs from a directory with weak write permissions accessible to local or network users
-
Inspect for unexpected DLL files in NetExtender folderList all .dll files in the NetExtender installation directory and compare against known legitimate DLLs (such as netextender.dll, neutil.dll, sslvpn.dll). Look for recently modified or newly created DLLs that you did not install.Affected if Unknown DLL files exist in the NetExtender directory, or known DLLs have been recently modified without an update
-
Check for NetExtender running with elevated privilegesOpen Task Manager, find the netextender.exe process, right-click and select 'Run as administrator' status. Also check the Windows Event Viewer for any suspicious process spawn events from NetExtender.Affected if NetExtender runs with administrator or SYSTEM privileges and vulnerable DLL loading paths exist
Your environment is affected if SonicWall NetExtender version 9.0.815 or earlier is installed and untrusted users can write to directories from which the application loads DLLs.
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 SonicWall NetExtender Windows client to a version newer than 9.0.815. If immediate patching is not possible, restrict write access to the directories from which NetExtender loads DLLs and monitor for unauthorized file modifications.
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-5131 — 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-2020-5131 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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
- No spam, self-promotion, credentials, or personal data