A vulnerability exists in the ASN.1 protocol library used by the Windows operating system. This flaw allows a hostile BITSTRING ASN.1 sequence to overwrite sections of heap memory remotely through any service which parses ASN.1 data. Examples of affected services include NetBIOS, SMB, IPSEC, Kerberos, SSL, and IIS. With a specially crafted request, an attacker can execute code with the privileges of the processing component, resulting in a loss of integrity.

Microsoft has released a patch to address this vulnerability, there are currently no known workarounds.

• Secunia Advisory ID: 10759
• Milw0rm: 153
• Exploit Database: 153
• CVE ID: 2003-0818 (see also: NVD)
• Microsoft Knowledge Base Article: 252648
• Metasploit ID: 3902
• Other Advisory URL: http://archives.neohapsis.com/archives/bugtraq/2004-02/0268.html
  http://research.eeye.com/html/advisories/published/AD20040210-2.html
  http://www.eeye.com/html/Research/Advisories/AD20040210-2.html [ Link is 404 ]
  http://www.foundstone.com/products/sa/fs-sa-02-10-04.pdf
• Generic Exploit URL: http://immunitysec.com
  http://metasploit.com/projects/Framework/modules/exploits/msasn1_ms04_007_killbill.pm
• Vendor Specific Solution URL: http://www.microsoft.com/downloads/details.aspx?FamilyId=0CC30297-D4AE-48E9-ACD0-1343D89CCBBA&displaylang=en
  http://www.microsoft.com/downloads/details.aspx?FamilyId=191853C4-A4D2-4797-A8C6-A2E663A53698&displaylang=en
  http://www.microsoft.com/downloads/details.aspx?FamilyId=383C397F-9318-4AD5-9C2C-0577118A1E68&displaylang=en
  http://www.microsoft.com/downloads/details.aspx?FamilyId=3D7FFFF9-A497-42FF-90E7-283732B2E117&displaylang=en
  http://www.microsoft.com/downloads/details.aspx?FamilyId=92400199-B3D5-4826-98D4-F134849F5249&displaylang=en
  http://www.microsoft.com/downloads/details.aspx?FamilyId=D83B39D3-FF13-4D0B-B406-A225AED0D659&displaylang=en
  http://www.microsoft.com/downloads/details.aspx?FamilyId=FA280168-66E1-4B5F-958F-E178C3F61F7C&displaylang=en
• Microsoft Security Bulletin: MS04-007
• Keyword: MSASN1.DLL

• Derek Soeder - eEye Digital Security