Windows Search Service: Heap-based buffer overflow allows local privilege escalation
Summary
A heap-based buffer overflow in the Microsoft Windows Search Service allows a local, low-privileged user to elevate privileges. The flaw is not reachable from the internet. An attacker needs an existing foothold on the system, for example through a phished or compromised standard user account, a shared workstation or a terminal server.
Affected
- Windows 10 Version 1607 (below 10.0.14393.9612)
- Windows 10 Version 1809 (below 10.0.17763.9376)
- Windows 10 Version 21H2 (below 10.0.19044.7807)
- Windows 10 Version 22H2 (below 10.0.19045.7807)
- Windows 11 Version 23H2 (below 10.0.22631.7652)
- Windows 11 Version 24H2 (below 10.0.26100.9711)
- Windows 11 Version 25H2 (below 10.0.26200.9711)
- Windows 11 Version 26H1 (below 10.0.28000.3231)
- Windows 11 Version 26H2 (below 10.0.26300.9711)
- Windows Server 2012 and Server Core installation (below 6.2.9200.26434)
- Windows Server 2012 R2 and Server Core installation (below 6.3.9600.23470)
- Windows Server 2016 (below 10.0.14393.9612)
Fixed in
- Install the October 2026 cumulative update for each affected product, reaching at least the build numbers listed above (per CVE record ranges).
- Windows 10 Version 1607 and Windows Server 2016: build 10.0.14393.9612 or later.
- The KB numbers for these builds were not confirmed in the available sources; verify them on the MSRC Security Update Guide.
Workaround
Unknown.
Exploitation
- Not listed in CISA KEV.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- No public proof of concept found; EPSS about 0.3%.
Our recommendation
- Patch all affected Windows systems with the October 2026 cumulative update, prioritising Windows 10 1607 and Server 2016 hosts that are still in use, and multi-user systems.
- Check whether Windows 10 1607 systems still receive security updates; if the support has ended, plan an upgrade or check Extended Security Update eligibility.
- Limit local logon rights and keep standard user accounts protected against phishing.
- Verify the fixed build on MSRC before deployment.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Microsoft Windows Search Component
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation unlikely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5126651, KB5126655, KB5126657, KB5126646, KB5127648, KB5126653
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-83920 msrc.microsoft.com
- Vulners NVD record CVE-2026-83920 vulners.com
- Vulners MSCVE record MS:CVE-2026-83920 vulners.com
- OpenCVE CVE-2026-83920 app.opencve.io
- Qualys Patch Tuesday review October 2026 blog.qualys.com
- Strix CVE-2026-83920 www.strix.ai
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, 02:34.
Original description (NVD)
Heap-based buffer overflow in Microsoft Windows Search Component allows an authorized attacker to elevate privileges locally.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
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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