Microsoft Windows BITS: Elevation of privilege via integer overflow

Summary

An integer overflow or wraparound in the Windows Background Intelligent Transfer Service (BITS) allows an authorized local attacker to elevate privileges. According to Microsoft, a successful attack can grant SYSTEM privileges. The attacker needs a local account with low privileges, and no user interaction is required. Microsoft has released fixed builds for the affected Windows 10, Windows 11 and Windows Server versions. CISA's assessment lists exploitation as none, and no public exploit has been found.

Affected

• Windows 10 Version 1607 (10.0.14393.0 before 10.0.14393.9612)
• Windows Server 2016 (10.0.14393.0 before 10.0.14393.9612)
• Windows 10 Version 1809 (10.0.17763.0 before 10.0.17763.9376)
• Windows 10 Version 21H2 (10.0.19044.0 before 10.0.19044.7807)
• Windows 10 Version 22H2 (10.0.19045.0 before 10.0.19045.7807)
• Windows 11 Version 23H2 (10.0.22631.0 before 10.0.22631.7652)
• Windows 11 Version 24H2 (10.0.26100.0 before 10.0.26100.9711)
• Windows 11 Version 25H2 (10.0.26200.0 before 10.0.26200.9711)
• Windows 11 Version 26H1 (10.0.28000.0 before 10.0.28000.3231)
• Windows 11 Version 26H2 (10.0.26300.0 before 10.0.26300.9711)
• Windows Server 2012 (6.2.9200.0 before 6.2.9200.26434)
• Windows Server 2012 R2 (6.3.9600.0 before 6.3.9600.23470)

Fixed in

• Update to the October 2026 security update for your Windows version, which provides the builds listed as fixed by Microsoft (for example 10.0.14393.9612 for Windows 10 Version 1607 and Windows Server 2016).
• Verify the KB number on the Microsoft Security Update Guide before deployment. Tenable lists KB5126868 for Windows 10 Version 1607 and Windows Server 2016, but this was not confirmed on the MSRC page.

Workaround

• Unknown. No workaround or mitigation is documented in the sources. Apply the security update.

Exploitation

• No exploitation in the wild found.
• CISA ADP assessment: Exploitation none, Automatable no, Technical Impact total.
• EPSS score very low (0.00369).
• No public proof of concept found; this does not rule out that one exists.

Our recommendation

• Patch affected systems with the October 2026 security update, prioritizing multi-user Windows 10 Version 1607 and Windows Server 2016 hosts, such as shared workstations and terminal/RDS servers.
• Check whether Windows 10 Version 1607 is still supported; it is at or near end of service. Plan an upgrade if systems remain on it.
• Limit local accounts and review standard user privileges to reduce the risk of a foothold leading to SYSTEM.
• Monitor for unusual privilege escalation and check CISA KEV and public exploit sources for changes.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• Microsoft Security Update Guide: CVE-2026-88118 msrc.microsoft.com
• Talos: Microsoft Patch Tuesday for October 2026 blog.talosintelligence.com
• Qualys: Microsoft Patch Tuesday October 2026 review threatprotect.qualys.com
• OpenCVE: CVE-2026-88118 app.opencve.io
• Tenable: CVE-2026-88118 plugins www.tenable.com

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 2 Nov 2026, 01:23.