cbcvebase.
CVE-2018-8476
published 2018-11-14

CVE-2018-8476: A remote code execution vulnerability exists in the way that Windows Deployment Services TFTP Server handles objects in memory, aka "Windows Deployment…

PriorityP270critical9.8CVSS 3.0
AVNACLPRNUINSUCHIHAH
EPSS
63.29%
99.1th percentile
A remote code execution vulnerability exists in the way that Windows Deployment Services TFTP Server handles objects in memory, aka "Windows Deployment Services TFTP Server Remote Code Execution Vulnerability." This affects Windows Server 2012 R2, Windows Server 2008, Windows Server 2012, Windows Server 2019, Windows Server 2016, Windows Server 2008 R2, Windows 10 Servers.

Affected

26 ranges· showing 25
VendorProductVersion rangeFixed in
microsoftwindows_10_servers
microsoftwindows_server_2008
microsoftwindows_server_2008
microsoftwindows_server_2008
microsoftwindows_server_2008
microsoftwindows_server_2008
microsoftwindows_server_2008
microsoftwindows_server_2008_r2
microsoftwindows_server_2008_r2
microsoftwindows_server_2008_r2
microsoftwindows_server_2012
microsoftwindows_server_2012
microsoftwindows_server_2012_r2
microsoftwindows_server_2016
microsoftwindows_server_2016
microsoftwindows_server_2019
msrcwindows_server_2008_for_32-bit_systems_service_pack_2
msrcwindows_server_2008_for_itanium-based_systems_service_pack_2
msrcwindows_server_2008_for_x64-based_systems_service_pack_2
msrcwindows_server_2008_r2_for_itanium-based_systems_service_pack_1
msrcwindows_server_2008_r2_for_x64-based_systems_service_pack_1
msrcwindows_server_2012
msrcwindows_server_2012_r2
msrcwindows_server_2016
msrcwindows_server_2019

Detection & IOCsextracted from sources · hover to see the quote

filenamewdstftp.dll
processCTftp::ParseRequest
processCTftpPacket::ParseRequest
processCTptReadFile::_IOCompletionCallback
  • Detect anomalous TFTP RRQ packets that use both 'blksize' and 'windowsize' options simultaneously — this is the crafted request pattern used to trigger the UAF by populating more than two CacheBlocks before an ACK is received.
  • Monitor for unauthenticated TFTP Read Requests (RRQ) to the Windows Deployment Services server (UDP/69) originating from unexpected or unauthorized hosts on the LAN, as the vulnerability is pre-authentication and requires no credentials.
  • Alert on heap corruption or use-after-free exceptions in wdstftp.dll — specifically when RAX points to freed memory during IOCompletionCallback execution, as this is the crash signature of the vulnerability.
  • Check Point IPS blade signature 'Microsoft Windows Deployment Services TFTP Server Code Execution (CVE-2018-8476)' can be used for network-level detection.
  • Monitor for unusual RPC requests to wdssrv.dll from the same source as TFTP anomalies — the exploit chain involves using the WDS RPC interface (CRpcHandler::OnRecvRequest) as a heap-spray primitive targeting heap bucket size 0x5c-0x78.
  • ·The UAF is a race condition — exploitation success depends on server load and timing. A busy server handling large volumes of file read/write requests increases the attacker's chance of winning the race.
  • ·The CacheBlock linked list is hard-coded to a maximum of two nodes; exceeding this limit triggers tail deletion and the UAF condition — this is a fixed architectural constraint in the vulnerable wdstftp.dll.

CVSS provenance

nvdv3.09.8CRITICALCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.010.0CRITICALAV:N/AC:L/Au:N/C:C/I:C/A:C
vendor_msrc8.1HIGH
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