Windows Server FSRM: Heap-based buffer overflow enables privilege escalation
Summary
The Windows File Server Resource Management Service (FSRM) contains a heap-based buffer overflow that allows an authorized local user to elevate privileges. A successful attacker can gain full control over confidentiality, integrity and availability on the affected server. The attacker needs a valid local account or code execution on the system first, so the flaw is not directly reachable from the internet.
Affected
- Windows Server 2016 and Server Core installation: 10.0.14393.0 to before 10.0.14393.9688
- Windows Server 2019 and Server Core installation: 10.0.17763.0 to before 10.0.17763.9487
- Windows Server 2022: 10.0.20348.0 to before 10.0.20348.5870
- Windows Server 2025 and Server Core installation: 10.0.26100.0 to before 10.0.26100.33822
- Windows client editions: Unknown.
Fixed in
- Install the November 2026 security update for the affected Windows Server versions.
- Fixed builds according to the CVE record: 10.0.14393.9688 (2016), 10.0.17763.9487 (2019), 10.0.20348.5870 (2022), 10.0.26100.33822 (2025).
- Verify the exact KB and build list on the Microsoft Security Update Guide.
Workaround
Unknown. No workaround is documented in the sources reviewed; applying the security update is the fix.
Exploitation
- No known in-the-wild exploitation or public proof-of-concept at the time of research.
- CISA SSVC assessment: exploitation none, not automatable, total technical impact.
- CVSS temporal metric E:U (Exploit Code Maturity: Unproven).
Our recommendation
- Install the November 2026 cumulative update on all Windows Server 2016, 2019, 2022 and 2025 systems, starting with file servers.
- Check whether FSRM is installed, for example with Get-WindowsFeature FS-Resource-Manager.
- Confirm the fixed builds and exploitation status on the Microsoft Security Update Guide before rollout.
- Restrict local logon rights and monitor servers for unexpected privilege changes.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows File Server Resource Management Service
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5131291, KB5131085, KB5131090, KB5131080, KB5131077
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE Record CVE-2026-113765 (CVE.org) www.cve.org
- Microsoft Security Update Guide CVE-2026-113765 msrc.microsoft.com
- Strix.ai CVE-2026-113765 (third-party tracker) www.strix.ai
- Microsoft Patch Tuesday November 2026 (Cisco Talos) blog.talosintelligence.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 11 Nov 2026, 04:11.
Original description (NVD)
Heap-based buffer overflow in Windows File Server Resource Management Service 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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