CVE-2003-0818
HighExploitedPublic exploitMultiple 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…
Published Mar 3, 2004 · Updated Apr 15, 2026
Key Facts
Patch immediately- CVE-2003-0818 is a high-severity vulnerability (CVSS 7.5 v2) affecting Windows 2000 (Microsoft), Windows 2003 Server (Microsoft), Windows Nt (Microsoft) and 1 more product.
- It is exploited in the wild, listed in Industry KEV feed since Apr 26, 2016. Public exploit code is available.
- EPSS estimates a 82% probability of exploitation in the next 30 days.
- No fixed version is listed yet; check the vendor advisory for mitigations.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v2
7.5
AV:N/AC:L/Au:N/C:P/I:P/A:P
EPSS (30-day exploit likelihood)
82%
Higher than 99.6% of all scored CVEs
Exploited in the wild
Yes
1 catalog listing
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2003-0818 brief as a PDF
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Description
Multiple 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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| Industry KEV feed | Apr 26, 2016 | n/a | Not reported |
Required action: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Affected Products
38 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Windows 2000Microsoft | See advisory | n/a |
| Windows 2003 ServerMicrosoft | enterprise, enterprise_64-bit, r2, standard, web | n/a |
| Windows NtMicrosoft | 4.0, 4.0-sp1, 4.0-sp2, 4.0-sp3, 4.0-sp4, 4.0-sp5, 4.0-sp6a, 4.0-sp6 | n/a |
| Windows XpMicrosoft | See advisory | n/a |
Timeline
Publicly disclosed
Mar 3, 2004
Added to Industry KEV feed
Apr 26, 2016
Last updated
Apr 15, 2026
References
- advisoryVU#216324
- exploitVulnCheck exploitation report
- exploitMSF ms04_007_killbill.rb
- exploitExploitDB-153
- exploitExploitDB-16377
FAQ
Common Questions.
Multiple 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…
Affected: Windows 2000 (Microsoft); Windows 2003 Server (Microsoft) versions enterprise, enterprise_64-bit, r2, standard, web; Windows Nt (Microsoft) versions 4.0, 4.0-sp1, 4.0-sp2, 4.0-sp3, 4.0-sp4, 4.0-sp5, 4.0-sp6a, 4.0-sp6, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in Industry KEV feed since Apr 26, 2016.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
Public exploit code is available.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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