CVE-2000-0457
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 · uneditedISM.DLL in IIS 4.0 and 5.0 allows remote attackers to read file contents by requesting the file and appending a large number of encoded spaces (%20) and terminated with a .htr extension, aka the ".HTR File Fragment Reading" or "File Fragment Reading via .HTR" 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 confidenceISM.DLL in IIS 4.0 and 5.0 contains a vulnerability that allows remote attackers to read arbitrary file contents by requesting a target file appended with a large number of encoded spaces (%20) and terminated with a .htr extension. This file fragment reading vulnerability is caused by improper handling of the .HTR request handler, allowing unauthenticated network attackers to potentially disclose sensitive files from the web server's filesystem.
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= 4.0= 5.0CVSS 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
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:L/Au:N/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 versionCheck the Windows system for IIS version: On IIS 4.0 (Windows NT 4.0 Option Pack), check in Internet Service Manager. On IIS 5.0 (Windows 2000), check in Computer Management > Services > IIS. The version appears in the IIS snap-in or run 'iisreset /status' or check the metabase.Affected if Version is exactly 4.0 or exactly 5.0 (not newer versions)
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Verify .HTR extension mapping is enabledOpen IIS Metabase Explorer (from IIS Resource Kit) or use adsutil.vbs to query the script map: cscript adsutil.vbs get W3SVC/1/Root/ScriptMap | findstr ".htr" or check the Script Maps for the affected website in IIS Manager.Affected if The .HTR extension mapping exists and points to ISM.DLL (typically as an ISAPI extension)
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Confirm ISM.DLL exists on the systemSearch for ISM.DLL in the system. Default path on IIS 4.0 is C:\winnt\system32\inetsrv\ism.dll and on IIS 5.0 is C:\windows\system32\inetsrv\ism.dll. Use File Explorer or run 'dir /s C:\ism.dll'.Affected if ISM.DLL file exists in the inetsrv directory (indicates the vulnerable component is installed)
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Test for vulnerable .htr request handlingSend an HTTP request to the IIS server with a path like /anything%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20.htr and observe the response. Use curl or a browser. The vulnerability allows reading file fragments when .HTR handler processes the request.Affected if The server returns file contents or a response indicating the .htr request was processed (not a 404 error)
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Check if .HTR ISAPI extension is registeredQuery the IIS metabase for ISAPI extension registration: cscript adsutil.vbs enum /W3SVC/1/Root or check the ISAPI Extensions filter in IIS Manager under Web Service Extensions.Affected if ISM.DLL is listed as a registered ISAPI extension or filter
A system is affected if it runs IIS 4.0 or 5.0 with the .HTR extension mapping enabled and ISM.DLL present, and the server processes .htr requests without returning a 404 error.
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 dataDisable the .HTR extension mapping in IIS or remove/unregister the ISM.DLL ISAPI extension entirely if .htr functionality is not required, as this vulnerability allows unauthenticated remote file disclosure.
- Consultation1.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2000-0457 — 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-2000-0457 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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- Version or environment caveats, and links to real fixes
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