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Microsoft OpenSSH for Windows: Use after free leads to remote code execution

CVE-2026-97816Critical 9.8

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Summary

Microsoft OpenSSH for Windows contains a use-after-free flaw (CWE-416), tracked as CVE-2026-97816. An unauthenticated attacker on the network can exploit it to execute code, as reflected in the CVSS score of 9.8. No credentials or user interaction are required, so network reachability of the service is the main condition. MSRC labels the severity as Important, which differs from the NVD score.

Affected

  • Windows 10 Version 1809 and Windows Server 2019 (including Server Core): 10.0.17763.0 to below 10.0.17763.9376
  • Windows 10 Version 21H2: 10.0.19044.0 to below 10.0.19044.7807
  • Windows 10 Version 22H2: 10.0.19045.0 to below 10.0.19045.7807
  • Windows 11 Version 23H2: 10.0.22631.0 to below 10.0.22631.7652
  • Windows 11 Version 24H2: 10.0.26100.0 to below 10.0.26100.9711
  • Windows 11 Version 25H2: 10.0.26200.0 to below 10.0.26200.9711
  • Windows 11 Version 26H1: 10.0.28000.0 to below 10.0.28000.3231
  • Windows 11 Version 26H2: 10.0.26300.0 to below 10.0.26300.9711
  • Windows Server 2022: 10.0.20348.0 to below 10.0.20348.5761
  • Windows Server 2025 (including Server Core): 10.0.26100.0 to below 10.0.26100.33650

Source: CVE record ranges. Not yet verified against MSRC.

Fixed in

Unknown until confirmed on MSRC.

  • The upper bounds of the CVE record ranges (for example 10.0.17763.9376 for Windows 10 1809 and Server 2019) are the presumed first fixed builds.
  • KB numbers: Unknown.

Workaround

  • Unknown. No vendor workaround found.
  • If the OpenSSH server is not needed, disable it.
  • If it is needed, restrict TCP port 22 to management networks with firewall rules and do not expose it to the internet.

Exploitation

  • No evidence of exploitation in the wild found.
  • Rapid7 rates exploitation as Less Likely.
  • CISA SSVC: exploitation none, automatable yes, technical impact total.
  • No public proof of concept found; this does not prove that none exists.

Our recommendation

  • Inventory Windows hosts with the OpenSSH feature enabled and check whether they are reachable from the internet or untrusted networks.
  • Disable the OpenSSH server where it is not needed.
  • Patch internet-facing systems first and apply the October 2026 OpenSSH for Windows fixes together with the related SSH flaws.
  • Check whether Windows 10 1809 and Server 2019 systems are still supported.
  • Re-check exploitation status in a few days.

Information from Microsoft (Patch Tuesday October 2026)

Severity (Microsoft)
Important
Impact
Remote code execution – OpenSSH for Windows
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, KB5126657, KB5126655, KB5126653, KB5127648, KB5126646

Entry in the Microsoft Security Update Guide

Public exploits

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

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 30 Oct 2026, 18:10.

Original description (NVD)

Use after free in OpenSSH for Windows allows an unauthorized attacker to execute code over a network.

NVD references (1)

Sources

The tracker combines official, freely usable data sources – updated continuously:

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.

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