dbcve.org
W3who.dllApplication · Microsoft

CVE-2004-1134

HIGH · 10.0 CVSS v2.0 Published 2005-01-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
High EPSS Remotely reachable No privileges Zero-click

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 · unedited
Buffer overflow in the Microsoft W3Who ISAPI (w3who.dll) allows remote attackers to cause a denial of service and possibly execute arbitrary code via a long query string.

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 confidence

Buffer overflow vulnerability in the Microsoft W3Who ISAPI extension (w3who.dll) allows remote attackers to cause a denial of service and potentially execute arbitrary code by sending a specially crafted long query string to the affected DLL.

MitigationRemove or disable the vulnerable w3who.dll ISAPI extension from IIS if not required, or apply any available Microsoft security updates for this component.

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
W3who.dllApplication
Affected:all versions

CVSS 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
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:L/Au:N/C:C/I:C/A:C

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 checks

Work through these to decide whether this CVE applies to you.

  1. Locate w3who.dll on the system
    Search for w3who.dll in common IIS directories: %SystemRoot%\system32\inetsrv, %SystemRoot%\system32\inetsrv\w3who.dll, or search the entire web root directories using 'dir /s /b w3who.dll' command
    Affected if The file w3who.dll exists on the server
  2. Check if the ISAPI extension is registered in IIS
    Use the IIS Metabase Explorer (metabase.xml) or run 'cscript adsutil.vbs enum /w3svc' to check for ISAPI extension mappings that reference w3who.dll, or inspect %SystemRoot%\system32\inetsrv\Metabase.xml for entries containing 'w3who'
    Affected if The ISAPI extension w3who.dll is registered in IIS configuration
  3. Verify the extension is enabled in IIS
    Check IIS Manager for the w3who.dll extension under 'ISAPI and CGI Restrictions' or inspect the Web Service Extensions folder to confirm the extension is allowed
    Affected if The w3who.dll ISAPI extension is listed as allowed or enabled in IIS
  4. Check if the extension responds to requests
    Send an HTTP request to the w3who.dll endpoint (for example: http://yourserver/scripts/w3who.dll or check common virtual directories) with a test query string and verify the server responds
    Affected if The server accepts and processes requests to w3who.dll

The server is affected if w3who.dll exists, is registered as an ISAPI extension in IIS, and the extension is enabled to process requests.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Remove or disable the vulnerable w3who.dll ISAPI extension from IIS if not required, or apply any available Microsoft security updates for this component.

Recommended fix High confidence
  1. Identify all IIS servers running w3who.dll by searching the web root directories for the file
  2. Locate the IIS metabase or application host configuration to find where w3who.dll is mapped as an ISAPI extension
  3. Remove the ISAPI extension mapping for w3who.dll in IIS Manager (go to the website or application, open 'Handler Mappings', find the w3who.dll entry, and remove it)
  4. Delete the w3who.dll file from the server filesystem
  5. Restart IIS (run 'iisreset' from an elevated command prompt)
  6. Verify the ISAPI extension is no longer accessible by attempting to request it (e.g., http://server/w3who.dll?anything) - it should return a 404 error
  7. Audit other ISAPI extensions installed on the server and remove any that are unused, debug tools, or samples not intended for production use
Caveat Removing this extension will not break legitimate functionality as w3who.dll was a debugging/diagnostic ISAPI extension never intended for production use

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in W3who.dll Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2004-1134 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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