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Isa ServerApplication · Microsoft

CVE-2003-0526

MEDIUM · 6.8 CVSS v2.0 Published 2003-08-18
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
77/100
Remediation priority · High
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
Cross-site scripting (XSS) vulnerability in Microsoft Internet Security and Acceleration (ISA) Server 2000 allows remote attackers to inject arbitrary web script via a URL containing the script in the domain name portion, which is not properly cleansed in the default error pages (1) 500.htm for "500 Internal Server error" or (2) 404.htm for "404 Not Found."

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

Microsoft ISA Server 2000 contains a reflected cross-site scripting vulnerability in its default error pages (500.htm and 404.htm). The error pages do not properly sanitize the domain name portion of URLs before displaying them in the error message, allowing attackers to inject arbitrary JavaScript or HTML via a specially crafted URL.

MitigationUpdate the error page templates (500.htm and 404.htm) to properly HTML-encode all user-supplied input, specifically the domain name from the request URL before rendering it in the error response.

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
Isa ServerApplication
Affected:= 2000

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
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 checks

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

  1. Confirm ISA Server 2000 is installed
    Check the Windows registry under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ISAServer\CurrentVersion for the ProductVersion value, or check Add/Remove Programs for Microsoft ISA Server 2000.
    Affected if The installed version is Microsoft ISA Server 2000 exactly.
  2. Locate the error page files
    Navigate to the ISA Server installation directory and locate the error page templates, typically named 500.htm and 404.htm in the ErrorPages folder.
    Affected if The default error pages 500.htm and 404.htm exist in the ISA Server directory.
  3. Inspect the 500.htm error page source
    Open 500.htm in a text editor and search for any code that inserts or echoes the request URL or domain name into the HTML output without HTML encoding.
    Affected if The 500.htm file contains code that renders the domain name from the request URL without proper HTML encoding.
  4. Inspect the 404.htm error page source
    Open 404.htm in a text editor and search for any code that inserts or echoes the request URL or domain name into the HTML output without HTML encoding.
    Affected if The 404.htm file contains code that renders the domain name from the request URL without proper HTML encoding.
  5. Test the error pages with a crafted URL
    Send an HTTP request to the ISA Server with a specially crafted Host header or URL containing a script tag (for example, <script>alert(1)</script>) and observe whether it is reflected unescaped in the error response.
    Affected if The error page reflects the injected script or HTML tags back to the browser without encoding.

You are affected if Microsoft ISA Server 2000 is installed and the default 500.htm or 404.htm error pages are in use with code that displays the request domain name without HTML encoding.

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

Update the error page templates (500.htm and 404.htm) to properly HTML-encode all user-supplied input, specifically the domain name from the request URL before rendering it in the error response.

Fix this in Isa Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,780
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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-2003-0526 in production — separate from our analysis above.

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What this is

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What belongs here
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