CVE-2003-0768
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 ASP.Net 1.1 allows remote attackers to bypass the Cross-Site Scripting (XSS) and Script Injection protection feature via a null character in the beginning of a tag name.
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 confidenceIn ASP.NET 1.1, the XSS protection mechanism failed to properly sanitize input containing a null character (%00) at the beginning of HTML tag names. Attackers could craft malicious scripts that bypassed the built-in script injection filters because the validation logic did not handle null byte prefixes correctly, while browsers would still process the resulting HTML.
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= 1.1CVSS 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
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:M/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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Check ASP.NET versionInspect theCLR version or check the Microsoft .NET Framework version installed. In IIS, right-click the application pool or site and view the .NET CLR version, or run 'reg query "HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP\v1.1.4322" /v Install' at the command prompt.Affected if The installed version is ASP.NET 1.1 (NET CLR version 1.1.4322).
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Confirm built-in request validation is enabledCheck the web.config file for the application. Look for the element <pages validateRequest="true"> within the system.web section, or verify the Machine-level web.config for the same setting.Affected if validateRequest is set to true (the default), meaning the built-in XSS filter is active.
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Test null byte injection in input fieldsSubmit a test request with a parameter containing %00<script> or %00<img to any input field or query parameter. Capture the response and inspect whether the null character prefix is stripped before validation or if the tag is still present in the output.Affected if The null byte prefix is not stripped and the unescaped tag or script content appears in the response, indicating the filter can be bypassed.
You are affected if you are running ASP.NET 1.1 with validateRequest enabled and your application does not strip null characters before input processing, allowing %00-prefixed HTML tags to bypass the built-in XSS filter.
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 dataImplement input validation that strips or rejects null characters before processing, or upgrade to a patched version of ASP.NET. Additionally, deploy a Web Application Firewall (WAF) with XSS rules that handle null byte injection scenarios.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2003-0768 — 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-2003-0768 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
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