CVE-2021-33527
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 · uneditedIn MB connect line mbDIALUP versions <= 3.9R0.0 a remote attacker can send a specifically crafted HTTP request to the service running with NT AUTHORITY\SYSTEM that will not correctly validate the input. This can lead to an arbitrary code execution with the privileges of the service.
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 confidencembDIALUP versions 3.9R0.0 and earlier contain an input validation flaw in the HTTP request handling that allows remote attackers to achieve arbitrary code execution. The service runs with NT AUTHORITY\SYSTEM privileges, meaning any successful exploit grants the attacker full administrative control over the affected Windows system.
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<= 3.9r0.0CVSS 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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Verify if mbDIALUP service is installedCheck for mbDIALUP or mbconnectline services in Windows Services console (services.msc) or run: Get-Service | Where-Object {$_.Name -like '*mbDIALUP*' -or $_.DisplayName -like '*mbDIALUP*'}Affected if The service exists on the system, proceed to version check.
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Determine installed mbDIALUP versionCheck the version of the mbDIALUP executable or the installed software. Common locations: C:\Program Files\mbconnectline\mbDIALUP\ or check Programs and Features. Run: Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*' | Where-Object {$_.DisplayName -like '*mbDIALUP*'} | Select-Object DisplayName, DisplayVersionAffected if Version is 3.9R0.0 or lower, the system is within the affected range.
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Confirm the HTTP management interface is accessibleAttempt to access the mbDIALUP HTTP service locally: curl http://localhost:port (default ports vary, check documentation or netstat for listening ports). Alternatively run: netstat -ano | findstr LISTENING | findstr :[port]Affected if HTTP service is listening and reachable, the vulnerable code path is exposed.
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Check service account privilegesVerify the mbDIALUP service runs under NT AUTHORITY\SYSTEM: sc qc mbDIALUP (or the service name found) and check the SERVICE_START_NAME fieldAffected if Service runs as NT AUTHORITY\SYSTEM, any successful exploit grants full administrative control per the CVE description.
The system is affected if mbDIALUP version 3.9R0.0 or earlier is installed, the HTTP interface is accessible, and the service runs with elevated privileges.
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 dataApply the vendor-supplied patch or upgrade to a version beyond 3.9R0.0 that addresses the input validation vulnerability. If immediate patching is not possible, restrict network access to the mbDIALUP service to minimize exposure.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-33527 — 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-2021-33527 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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