CVE-2011-0040
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 · uneditedThe server in Microsoft Active Directory on Windows Server 2003 SP2 does not properly handle an update request for a service principal name (SPN), which allows remote attackers to cause a denial of service (authentication downgrade or outage) via a crafted request that triggers name collisions, aka "Active Directory SPN Validation Vulnerability."
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 confidenceThis is a denial-of-service vulnerability in Microsoft Active Directory on Windows Server 2003 SP2. The vulnerability exists in the SPN (Service Principal Name) validation logic, where the server fails to properly handle update requests that trigger name collisions. Remote attackers can send crafted SPN update requests causing authentication degradation or complete service outage.
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 dataall versionsCVSS 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
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 Windows Server 2003 is runningRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to confirm the Windows version. Look for Windows Server 2003 in the output.Affected if The system is running any version of Windows Server 2003 (this is the only affected product).
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Confirm Active Directory is installedCheck if the Active Directory Domain Services role is present. On Windows Server 2003, this can be verified by checking for the existence of the Ntds.dit database file in %SystemRoot%\Ntds or by checking 'Add/Remove Programs' for Active Directory domain controller role installation.Affected if Active Directory Domain Services is installed and running on the Windows Server 2003 system (the vulnerability only affects AD).
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Check if security update KB2509553 is installedRun 'wmic qfe list' or check 'Control Panel > Add or Remove Programs' > 'Show updates' to see if KB2509553 is listed among installed updates.Affected if KB2509553 is NOT installed - the system remains vulnerable and would be affected by the SPN validation flaw.
A system is affected if it runs Windows Server 2003 with Active Directory installed and KB2509553 has not been applied.
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 Microsoft security update KB2509553 (or subsequent superseding updates) to Windows Server 2003 SP2. If running Windows Server 2003, consider migration to a supported platform as extended support has ended.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2011-0040 — 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-2011-0040 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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