CVE-2001-0004
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 · uneditedIIS 5.0 and 4.0 allows remote attackers to read the source code for executable web server programs by appending "%3F+.htr" to the requested URL, which causes the files to be parsed by the .HTR ISAPI extension, aka a variant of the "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 confidenceIIS 4.0 and 5.0 contains a vulnerability in the .HTR ISAPI extension where specially crafted requests with '%3F+.htr' appended to the URL cause the server to return the source code of executable web programs rather than executing them. The .HTR extension improperly parses the request, treating it as a file read operation instead of a program 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= 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
- None
- Availability
- None
AV:N/AC:L/Au:N/C:P/I:N/A:N
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.
-
Identify the IIS versionCheck the IIS version via registry key 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\InetStp' (Value: 'VersionString') or by running 'iisinfo' or checking IIS Manager propertiesAffected if The version is 4.0 or 5.0 specifically
-
Verify the .HTR ISAPI extension is loadedCheck the IIS metabase or registry for the presence of the .HTR extension mapping under 'HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters\Script Map' or view via IIS Manager under 'Script Maps'Affected if The .HTR extension handler is present and mapped to 'htr.dll'
-
Confirm HTR handler is enabled at the global or site levelUse IIS Metabase Explorer or adsutil.vbs to query the 'ScriptMaps' property for '.htr' entries at the root level or specific sitesAffected if A script map entry exists for '.htr' pointing to an ISAPI DLL (typically 'htr.dll')
You are affected if you are running IIS 4.0 or 5.0 AND the .HTR ISAPI extension with its script mapping is still installed and enabled on the server.
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 or remove the .HTR ISAPI extension in IIS, or migrate from these deprecated IIS versions to supported versions. This is a critical legacy system vulnerability; affected IIS 4.0/5.0 installations should be retired or upgraded as they are no longer supported by Microsoft.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 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 $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2001-0004 — 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-2001-0004 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