CVE-2003-0818
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 · uneditedMultiple integer overflows in Microsoft ASN.1 library (MSASN1.DLL), as used in LSASS.EXE, CRYPT32.DLL, and other Microsoft executables and libraries on Windows NT 4.0, 2000, and XP, allow remote attackers to execute arbitrary code via ASN.1 BER encodings with (1) very large length fields that cause arbitrary heap data to be overwritten, or (2) modified bit strings.
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 confidenceInteger overflows in Microsoft's ASN.1 library (MSASN1.DLL) when parsing BER-encoded ASN.1 data allow remote attackers to execute arbitrary code. The overflows occur when processing very large length fields that corrupt heap memory or when handling modified bit strings, affecting critical components like LSASS.EXE and CRYPT32.DLL.
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 dataall versions= enterprise= enterprise_64-bit= r2= standard= web= 4.0all versionsCVSS 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
- Partial
- Availability
- Partial
AV:N/AC:L/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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Identify Windows versionRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to determine the installed Windows versionAffected if The version is Windows 2000 (any), Windows 2003 Server (any edition), Windows NT 4.0, or Windows XP (any)
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Check MSASN1.DLL versionLocate MSASN1.DLL in the system directory (typically C:\Windows\System32\) and view its version properties, or run 'dir MSASN1.DLL /s' to find all instances and use 'powershell (Get-Item "C:\Windows\System32\MSASN1.DLL").VersionInfo' to read version detailsAffected if The DLL version is present on an unpatched Windows 2000, 2003, NT 4.0, or XP system - compare against known affected versions for this CVE
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Verify crypt32.dll is presentCheck for the presence of CRYPT32.DLL in the system directory using 'dir C:\Windows\System32\CRYPT32.DLL' or verify via 'powershell Test-Path C:\Windows\System32\CRYPT32.DLL'Affected if CRYPT32.DLL exists on the system (this component uses the vulnerable ASN.1 library for certificate parsing)
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Verify lsass.exe is presentCheck for LSASS.EXE in the system directory using 'dir C:\Windows\System32\lsass.exe' or view process list with 'tasklist | findstr lsass'Affected if LSASS.EXE exists (this is a critical process that uses the vulnerable MSASN1.DLL library)
The system is likely affected if it runs an unpatched Windows 2000, Windows 2003 Server, Windows NT 4.0, or Windows XP version that contains the vulnerable MSASN1.DLL library used by CRYPT32.DLL and LSASS.EXE.
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 dataApply Microsoft security update MS04-007 or subsequent cumulative patches for the affected Windows versions (NT 4.0, 2000, XP) to patch the vulnerable MSASN1.DLL library.
- Consultation1.0 h
- Implementation2.0 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 $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2003-0818 — 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-2003-0818 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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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
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