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Microsoft Windows: Heap overflow in Scripting Engine allows local privilege escalation

CVE-2026-88193High 7.8

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Summary

The Microsoft Scripting Engine component of Windows contains a heap-based buffer overflow (CWE-122), tracked as CVE-2026-88193. An attacker with local, low-privileged access can exploit it to elevate privileges, with high impact on confidentiality, integrity and availability. It is not reachable directly from the internet and requires a foothold on the system, such as a compromised user account or malware.

Affected

  • Windows 10 Version 1607 (builds 10.0.14393.0 to before 10.0.14393.9612)
  • Windows 10 Version 1809 (builds before 10.0.17763.9376)
  • Windows 10 Version 21H2 (builds before 10.0.19044.7807)
  • Windows 10 Version 22H2 (builds before 10.0.19045.7807)
  • Windows 11 Version 23H2 (builds before 10.0.22631.7652)
  • Windows 11 Version 24H2 (builds before 10.0.26100.9711)
  • Windows 11 Version 25H2 (builds before 10.0.26200.9711)
  • Windows 11 Version 26H1 (builds before 10.0.28000.3231)
  • Windows 11 Version 26H2 (builds before 10.0.26300.9711)
  • Windows Server 2012 and Server Core (builds before 6.2.9200.26434)
  • Windows Server 2012 R2 and Server Core (builds before 6.3.9600.23470)
  • Windows Server 2016 (builds before 10.0.14393.9612)
  • Version ranges per the CNA record; verify on MSRC before rollout.

Fixed in

  • Security update for each listed build, as stated in the Microsoft advisory.
  • Fixed builds per CNA record: 10.0.14393.9612 (1607 and Server 2016), 10.0.17763.9376 (1809), 10.0.19044.7807 (21H2), 10.0.19045.7807 (22H2), 10.0.22631.7652 (23H2), 10.0.26100.9711 (24H2), 10.0.26200.9711 (25H2), 10.0.28000.3231 (26H1), 10.0.26300.9711 (26H2), 6.2.9200.26434 (Server 2012), 6.3.9600.23470 (Server 2012 R2).
  • Specific KB article numbers for Windows 10 1607: Unknown.

Workaround

Unknown. No workaround was found in the sources checked. Install the security update.

Exploitation

  • CISA SSVC: exploitation none, not automatable, technical impact total.
  • Not listed in CISA KEV.
  • EPSS score about 0.30%.
  • No public proof of concept found in the searches performed; this does not exclude that one appears later.

Our recommendation

  • Inventory all Windows devices and servers, including Windows 10 1607 and Server 2016, and check whether they are still supported.
  • Apply the October 2026 cumulative security update from Microsoft for each build and reboot.
  • Prioritise multi-user systems such as terminal servers, file servers and Server 2016.
  • Retire unsupported Windows 10 1607 systems where possible.
  • Recheck exploitation status (KEV, public PoC) in the next patch cycle.

Information from Microsoft (Patch Tuesday October 2026)

Severity (Microsoft)
Important
Impact
Elevation of privilege – Microsoft Scripting Engine
Status on Patch Tuesday
Neither exploited nor publicly disclosed
Exploitability assessment
Exploitation less likely
Product family
Windows, Windows ESU (Extended Security Updates)
Updates (KB)
KB5126651, KB5126655, KB5126657, KB5126646, KB5127648, KB5126653

Entry in the Microsoft Security Update Guide

Public exploits

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

Research sources

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, 01:07.

Original description (NVD)

Heap-based buffer overflow in Microsoft Scripting Engine allows an authorized attacker to elevate privileges locally.

NVD references (1)

Sources

The tracker combines official, freely usable data sources – updated continuously:

This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.

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