CVE-2009-4445
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 · uneditedMicrosoft Internet Information Services (IIS), when used in conjunction with unspecified third-party upload applications, allows remote attackers to create empty files with arbitrary extensions via a filename containing an initial extension followed by a : (colon) and a safe extension, as demonstrated by an upload of a .asp:.jpg file that results in creation of an empty .asp file, related to support for the NTFS Alternate Data Streams (ADS) filename syntax. NOTE: it could be argued that this is a vulnerability in the third-party product, not IIS, because the third-party product should be applying its extension restrictions to the portion of the filename before the colon.
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 · moderate confidenceMicrosoft IIS, when used with third-party file upload applications, allows remote attackers to create empty files with dangerous extensions (like .asp) by exploiting NTFS Alternate Data Streams (ADS) syntax in filenames. A file uploaded as '.asp:.jpg' results in an empty .asp file being created on the server, which could then be executed.
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<= 6.0CVSS 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
- M
- Authentication
- Single
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:M/Au:S/C:P/I:P/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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Identify IIS versionRun 'iisreset' or check IIS Manager, or inspect the HTTP Server header via 'curl -I http://localhost', or check HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters in the registryAffected if Version is 6.0 or lower (IIS 6.0 and below)
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Determine if third-party file upload applications are in useReview the web application stack for any upload functionality (form-based file upload scripts, components, or modules). Check the web root directory for upload handling codeAffected if Any web application or module that accepts file uploads from users is present
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Inspect web root for suspicious files with dangerous extensionsUse 'dir /s /b C:\Inetpub\wwwroot\*.asp' (or relevant web root) to list all .asp files. Also check for unexpected file extensions like .aspx, .cer, .asaAffected if Any .asp or other executable extension files exist that were not deliberately placed there by administrators
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Look for files with ADS syntax in the filenameUse 'dir /r /s C:\Inetpub\wwwroot' to show alternate data stream files, or search for filenames containing colons using 'dir /s /b | findstr :' in the web rootAffected if Any files with colons in the filename (e.g., 'file.asp:.jpg') are present in the web directory tree
If running IIS 6.0 or lower with a third-party file upload application that does not sanitize filenames containing colons, and unexpected .asp or executable files are found in the web root, the environment is likely affected by this vulnerability.
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 dataValidate and sanitize all uploaded filenames in third-party upload applications to strip or reject filenames containing colon characters before processing, or configure IIS/web server to block ADS syntax in file uploads.
- Consultation6.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,680.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2009-4445 — 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-2009-4445 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
- No spam, self-promotion, credentials, or personal data