Microsoft Windows RRAS: Denial of service through out-of-bounds read
Summary
Microsoft has fixed an out-of-bounds read in the Windows Routing and Remote Access Service (RRAS) in October 2026. An unauthenticated attacker with network access can send crafted traffic to crash the service, causing a denial of service. The flaw has no confidentiality or integrity impact, and no exploitation in the wild is known.
Affected
- Windows 10 Version 1607 (builds 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 incl. Server Core (builds before 6.2.9200.26434)
- Windows Server 2012 R2 incl. Server Core (builds before 6.3.9600.23470)
- Windows Server 2016 (builds before 10.0.14393.9612)
Fixed in
- Windows 10 Version 1607: 10.0.14393.9612
- Windows 10 Version 1809: 10.0.17763.9376
- Windows 10 Version 21H2: 10.0.19044.7807
- Windows 10 Version 22H2: 10.0.19045.7807
- Windows 11 Version 23H2: 10.0.22631.7652
- Windows 11 Version 24H2: 10.0.26100.9711
- Windows 11 Version 25H2: 10.0.26200.9711
- Windows 11 Version 26H1: 10.0.28000.3231
- Windows 11 Version 26H2: 10.0.26300.9711
- Windows Server 2012: 6.2.9200.26434
- Windows Server 2012 R2: 6.3.9600.23470
- Windows Server 2016: 10.0.14393.9612
Exact KB numbers: check the MSRC advisory.
Workaround
Unknown. No Microsoft workaround was found. Restricting RRAS exposure at the network perimeter may reduce the risk (general practice, not from the vendor).
Exploitation
- Not listed in the CISA KEV catalog.
- CISA SSVC: exploitation none, automatable yes, technical impact partial.
- No public proof of concept found in the research. This does not rule one out.
- EPSS about 0.011 (aggregator data).
Our recommendation
- Patch RRAS servers and routing hosts to the fixed builds, starting with internet-facing and VPN servers.
- Check whether the RRAS role is actually in use before treating clients as urgent.
- Replace or upgrade Windows 10 Version 1607 systems if they are no longer supported.
- Check whether CVE-2026-85809 (remote code execution in the same component) is patched on the same hosts.
- Monitor RRAS services for crashes and unusual traffic.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Denial of service – Windows Routing and Remote Access Service (RRAS)
- 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
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide: CVE-2026-85808 msrc.microsoft.com
- Vulners NVD mirror: CVE-2026-85808 vulners.com
- Vulners MSCVE: MS:CVE-2026-85808 vulners.com
- OpenCVE: CVE-2026-85808 app.opencve.io
- Strix.ai: CVE-2026-85808 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, 18:34.
Original description (NVD)
Out-of-bounds read in Windows Routing and Remote Access Service (RRAS) allows an unauthorized attacker to deny service over a network.
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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