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.net FrameworkApplication · Microsoft

CVE-2007-0042

HIGH · 7.8 CVSS v2.0 Published 2007-07-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
87/100
Remediation priority · High
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
Interpretation conflict in ASP.NET in Microsoft .NET Framework 1.0, 1.1, and 2.0 for Windows 2000, XP, Server 2003, and Vista allows remote attackers to access configuration files and obtain sensitive information, and possibly bypass security mechanisms that try to constrain the final substring of a string, via %00 characters, related to use of %00 as a string terminator within POSIX functions but a data character within .NET strings, aka "Null Byte Termination 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 confidence

A null byte termination vulnerability in ASP.NET allows remote attackers to bypass security mechanisms by inserting %00 characters in requests. The %00 character acts as a string terminator in POSIX functions but remains as valid data in .NET, enabling attackers to access configuration files and obtain sensitive information that should be protected.

MitigationApply Microsoft security patches for the affected .NET Framework versions (1.0, 1.1, 2.0), or upgrade to supported .NET versions. Implement input validation to reject or properly sanitize null byte characters in user-supplied file paths.

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
.net FrameworkApplication
Affected:= 1.0= 1.1= 2.0

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
None
Availability
None

AV:N/AC:L/Au:N/C:C/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 checks

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

  1. Identify installed .NET Framework version
    Check the Windows Registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v1.0.3705 (1.0), v1.1.4322 (1.1), or v2.0.50727 (2.0) under HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP, or run 'reg query "HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP" /s' to list all installed versions
    Affected if The installed version is exactly 1.0, 1.1, or 2.0 (these are the affected versions)
  2. Verify ASP.NET is in use
    Check for the presence of IIS or ASP.NET development server handling requests, or look for aspnet_isapi.dll loaded in memory, or examine running services/worker processes named aspnet_wp.exe (IIS 6) or w3wp.exe with ASP.NET app pools
    Affected if ASP.NET is processing requests and the .NET version is 1.0, 1.1, or 2.0
  3. Identify applications accepting file path input
    Review web application source code, IIS metabase, or application configuration for handlers that process file paths from query strings, form inputs, or cookies. Look for code patterns like Request.QueryString["file"], Request.Form["path"], or similar path-handling operations
    Affected if The application accepts file path parameters from user input without explicit null byte filtering
  4. Test for null byte bypass in request handling
    Submit a test request with %00 appended to a file path parameter (e.g., /page.aspx?file=config%00.txt) and observe if the request is processed differently or if alternate file extensions are accepted
    Affected if The application responds to requests containing %00 characters in file path parameters without rejecting or sanitizing them

The environment is affected if it runs .NET Framework 1.0, 1.1, or 2.0 AND hosts ASP.NET applications that accept user-supplied file paths without filtering null byte characters.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply Microsoft security patches for the affected .NET Framework versions (1.0, 1.1, 2.0), or upgrade to supported .NET versions. Implement input validation to reject or properly sanitize null byte characters in user-supplied file paths.

Fix this in .net Framework Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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Scan for this in your stack

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dbcve dependency scanner

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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-2007-0042 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