Windows SMB Client: Elevation of privilege via heap-based buffer overflow
Summary
A heap-based buffer overflow in the Windows SMB Client allows an authorized local user to elevate privileges. An attacker needs a local foothold, such as a standard user account or a malicious process on the system, and the attack is rated as high complexity. Exploitation has not been confirmed, and no public proof of concept was found in the sources.
Affected
- Microsoft Windows 11 version 26H1 (ARM64 and x64)
- Build range 10.0.28000.0 to before 10.0.28000.3501 per the CNA record
- Other Windows versions are not listed in the sources; check MSRC for the full product list
Fixed in
- Build 10.0.28000.3501 or later (implied by the CNA record, not yet confirmed on the MSRC advisory)
Workaround
- Unknown. No vendor-confirmed workaround was found; the patch is the recommended fix.
Exploitation
- Exploited in the wild: not confirmed for this CVE. Microsoft's CISA SSVC assessment lists exploitation as none and automatable as no.
- Temporal metrics (CNA record): exploit maturity Unproven (E:U).
- CISA KEV: not found in the sources.
- Public proof of concept: none found.
Our recommendation
- Install the Windows 11 26H1 update with build 10.0.28000.3501 or later in the normal monthly patch cycle, after confirming the fixed build on the MSRC advisory.
- Prioritise shared workstations, terminal servers and jump hosts running Windows 11 26H1.
- Check which systems run Windows 11 26H1 and restrict local user accounts where possible.
- Monitor for signs of privilege escalation on these systems.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows SMB Client
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows
- Updates (KB)
- KB5132059
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE.org CNA record CVE-2026-112971 www.cve.org
- Microsoft Security Update Guide CVE-2026-112971 msrc.microsoft.com
- Talos Microsoft Patch Tuesday November 2026 blog.talosintelligence.com
- Strix aggregator CVE-2026-112971 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 11 Nov 2026, 09:11.
Original description (NVD)
Heap-based buffer overflow in Windows SMB Client 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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.