Multiple Vulnerabilities in Microsoft ASN.1 Library
Original issue date: February 10, 2004
Last revised: February 12, 2004
Source: US-CERT
Systems Affected
- Microsoft Windows NT 4.0
- Microsoft Windows NT 4.0 TSE
- Microsoft Windows 2000
- Microsoft Windows XP
- Microsoft Windows Server 2003
Overview
Multiple integer overflow vulnerabilities in the Microsoft Windows ASN.1 parser library could allow an unauthenticated, remote attacker to execute arbitrary code with SYSTEM privileges.
I. Description
Abstract Syntax Notation number One (ASN.1) is an international standard used to describe and transmit data packets between applications and across networks. Microsoft Security Bulletin MS04-007 announces a patch for multiple vulnerabilities in the Microsoft Windows ASN.1 library (msasn1.dll). According to information from eEye Digital Security, the vulnerabilities involve integer overflows and other flaws in integer arithmetic. More information is available in two vulnerability notes:
VU#216324 - Microsoft ASN.1 Library improperly decodes malformed ASN.1 length values
(Other resources: AD20040210, MS04-007, CAN-2003-0818)
VU#583108 - Microsoft ASN.1 Library improperly decodes constructed bit strings
(Other resources: AD20040210-2, MS04-007, CAN-2003-0818)
eEye has published two detailed advisories on these issues: AD20040210 and AD20040210-2.
Any application that loads the ASN.1 library could serve as an attack vector. In particular, ASN.1 is used by a number of cryptographic and authentication services such as X.509 certificates (SSL/TLS, S/MIME, IKE), Kerberos, and NTLMv2. The Local Security Authority Subsystem (lsass.exe) and a component of the CryptoAPI (crypt32.dll) use the vulnerable ASN.1 library. Both client and server systems are affected.
II. Impact
An unauthenticated, remote attacker could execute arbitrary code with the privileges of the process using the ASN.1 library. In the case of most server and authentication applications, an attacker could gain SYSTEM privileges.
III. Solution
Apply a patch
Apply the appropriate patch as specified by Microsoft Security Bulletin MS04-007.
Appendix A. Vendor Information
This appendix contains information provided by vendors. When vendors
report new information, this section is updated and the changes are
noted in the revision history. If a vendor is not listed below, we
have not received their comments.
Please see Microsoft Security Bulletin MS04-007.
Appendix B. References
These vulnerabilities were researched and reported by eEye Digital Security. Information from eEye and Microsoft was used in this document.
Feedback can be directed to the author, Art Manion.
Copyright 2004 Carnegie Mellon University. Terms of use
Revision History
February 10, 2004: Initial release
February 12, 2004: Added ASN.1 definition, updated description of applications that use ASN.1