Windows 11: Heap-based buffer overflow in RPC Runtime leads to privilege escalation
Summary
A heap-based buffer overflow in the Windows RPC Runtime allows an authorized local attacker to elevate privileges. The attacker needs local access and a valid low-privileged account, and no user interaction is required. Microsoft rates the issue Important and reported no public disclosure or exploitation at publication. Fixes are available for the affected Windows 11 versions.
Affected
- Windows 11 version 23H2: 10.0.22631.0 to before 10.0.22631.7582
- Windows 11 version 24H2: 10.0.26100.0 to before 10.0.26100.9445
- Windows 11 version 25H2: 10.0.26200.0 to before 10.0.26200.9445
- Windows 11 version 26H1: 10.0.28000.0 to before 10.0.28000.2954
Fixed in
- Windows 11 23H2: build 10.0.22631.7582 or later (third-party mirror lists KB5122880; verify on MSRC)
- Windows 11 24H2: build 10.0.26100.9445 or later (third-party mirror lists KB5124008; verify on MSRC)
- Windows 11 25H2: build 10.0.26200.9445 or later (third-party mirror lists KB5124008; verify on MSRC)
- Windows 11 26H1: build 10.0.28000.2954 or later (third-party mirror lists KB5124012; verify on MSRC)
Workaround
Unknown.
Exploitation
- Microsoft reported at publication: not publicly disclosed, not exploited
- CISA SSVC in the CVE record: exploitation none, not automatable, total technical impact
- EPSS about 0.0039 at last capture
Our recommendation
- Install the cumulative update for your Windows 11 build via Windows Update, WSUS or Intune, and confirm the build number against the MSRC advisory
- Prioritise multi-user systems, terminal servers and hosts where untrusted users or malware could run
- Check whether any Windows 11 23H2 Enterprise or Education devices are near end of servicing and plan upgrades using the Microsoft lifecycle page
- Monitor the MSRC page and CISA KEV for changes
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Response Center: CVE-2026-83518 msrc.microsoft.com
- NVD mirror on Vulners: CVE-2026-83518 vulners.com
- OpenCVE: CVE-2026-83518 app.opencve.io
- Strix: CVE-2026-83518 (third-party version data) 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, 03:41.
Original description (NVD)
Heap-based buffer overflow in RPC Runtime 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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