ADV180022High

Windows Denial of Service Vulnerability

Published
September 11, 2018
Last Modified
—

🔗 CVE IDs covered (1)

ADV180022 · pending

📋 Description

Microsoft is aware of a denial of service vulnerability (named "FragmentSmack" CVE-2018-5391) affecting Windows systems. An attacker could send many 8-byte sized IP fragments with random starting offsets, but withhold the last fragment and exploit the worst-case complexity of linked lists in reassembling IP fragments. A system under attack would become unresponsive with 100% CPU utilization but would recover as soon as the attack terminated. Recommended actions To protect your system from this vulnerability, Microsoft recommends that you take the following actions: Register for security notifications mailer to be alerted of content changes to this advisory. See Microsoft Technical Security Notifications. Test and apply security updates. See the Affected Products table to download and install the updates. If you cannot apply the security updates immediately, you can apply the workaround described in FAQ #1. FAQ

  1. What workaround(s) exist for this vulnerability? The following commands disable packet reassembly. Any out-of-order packets are dropped. There is a potential for packet loss when discarding out-of-order packets. Valid scenarios should not exceed more than 50 out-of-order fragments. We recommend testing prior to updating production systems. Netsh int ipv4 set global reassemblylimit=0 Netsh int ipv6 set global reassemblylimit=0 Further netsh guidance can be found at netsh.
  2. Is Azure affected? Azure fabric layer protections mitigate this vulnerability. This is blocked before traffic reaches Azure VMs.
  3. What can I do at the perimeter to block this attack? Review the perimeter device guidance and modify reassembly packet limits similar to the commands listed in FAQ #1.

🎯 Affected products31

  • Windows 10 Version 1607 for 32-bit Systems
  • Windows 10 Version 1607 for x64-based Systems
  • Windows 10 Version 1703 for 32-bit Systems
  • Windows 10 Version 1703 for x64-based Systems
  • Windows 10 Version 1709 for 32-bit Systems
  • Windows 10 Version 1709 for x64-based Systems
  • Windows 10 Version 1803 for 32-bit Systems
  • Windows 10 Version 1803 for x64-based Systems
  • Windows 10 for 32-bit Systems
  • Windows 10 for x64-based Systems
  • Windows 7 for 32-bit Systems Service Pack 1
  • Windows 7 for x64-based Systems Service Pack 1
  • Windows 8.1 for 32-bit systems
  • Windows 8.1 for x64-based systems
  • Windows RT 8.1
  • Windows Server 2008 R2 for Itanium-Based Systems Service Pack 1
  • Windows Server 2008 R2 for x64-based Systems Service Pack 1
  • Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)
  • Windows Server 2008 for 32-bit Systems Service Pack 2
  • Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
  • Windows Server 2008 for Itanium-Based Systems Service Pack 2
  • Windows Server 2008 for x64-based Systems Service Pack 2
  • Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)
  • Windows Server 2012
  • Windows Server 2012 (Server Core installation)
  • Windows Server 2012 R2
  • Windows Server 2012 R2 (Server Core installation)
  • Windows Server 2016
  • Windows Server 2016 (Server Core installation)
  • Windows Server, version 1709 (Server Core Installation)
  • +1 more not shown

✅ Remediation

KB4457138 (Security Update) KB4457128 (Security Update) KB4457142 (Security Update) KB4457132 (Security Update) KB4457131 (Security Update) KB4457144 (Monthly Rollup) KB4457145 (Security Only) KB4457129 (Monthly Rollup) KB4457143 (Security Only) KB4458010 (Monthly Rollup) KB4457984 (Security Only) KB4457135 (Monthly Rollup) KB4457140 (Security Only)

🔗 References (13)