iDefense Security Advisory 06.11.09 - Remote exploitation of an invalid free vulnerability in Microsoft Corp.'s Active Directory Server allows attackers to exhaust all virtual memory. According to section 2.4 of the IETF Request For Comments (rfc) 4514, LDAP requests can contain strings that have been encoded using hexadecimal encoding. When Active Directory on Windows 2000 encounters such a request, it fails to release the memory associated with the hexadecimal encoded portion of the request. By continually making such requests, an attacker can exhaust virtual memory on the targeted system. iDefense confirmed the existence of this vulnerability using a Windows 2000 SP4 domain controller with all patches available as of January 2008 applied. All versions of Active Directory installed on Windows 2000 are suspected to be vulnerable.
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