Integer underflow in the BowserWriteErrorLogEntry function in the Common Internet File System (CIFS) browser service in Mrxsmb.sys or bowser.sys in Active Directory in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, R2, and R2 SP1, and Windows 7 Gold and SP1 allows remote attackers to execute arbitrary code or cause a denial of service (system crash) via a malformed BROWSER ELECTION message, leading to a heap-based buffer overflow, aka "Browser Pool Corruption Vulnerability." NOTE: some of these details are obtained from third party information.