Friday February 03, 2017

New Windows 10 Zero Day Exploit Allows Attackers to Cause a System Crash

Carnegie Mellon's Vulnerability Notes Database has a new alert up for an exploit that can allow a remote attacker to crash a Windows 10 machine. This exploit apparently works by taking advantage of a bug in how Windows 10 handles the SMB file sharing protocol. The only currently known defense is to block outbound SMB ports. Let's hope Microsoft get this one patched ASAP.

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Microsoft Windows fails to properly handle traffic from a malicious server. In particular, Windows fails to properly handle a specially-crafted server response that contains too many bytes following the structure defined in the SMB2 TREE_CONNECT Response structure. By connecting to a malicious SMB server, a vulnerable Windows client system may crash (BSOD) in mrxsmb20.sys. We have confirmed the crash with fully-patched Windows 10 and Windows 8.1 client systems, as well as the server equivalents of these platforms, Windows Server 2016 and Windows Server 2012 R2.

Note that there are a number of techniques that can be used to trigger a Windows system to connect to an SMB share. Some may require little to no user interaction.