Microsoft Windows Schannel: Elevation of privilege via NULL pointer dereference

Summary

A NULL pointer dereference in the Windows Schannel TLS/SSL component allows an authorized local user to elevate privileges. Windows 10, Windows 11 and Windows Server 2012, 2012 R2 and 2016 are affected according to the CNA data. An attacker needs a local account with low privileges and no user interaction, so this is a privilege escalation step after an initial compromise, not a remote entry point.

Affected

• Windows 10 Version 1607 (10.0.14393.0 to below 10.0.14393.9612)\n- Windows 10 Version 1809 (10.0.17763.0 to below 10.0.17763.9376)\n- Windows 10 Version 21H2 (10.0.19044.0 to below 10.0.19044.7807)\n- Windows 10 Version 22H2 (10.0.19045.0 to below 10.0.19045.7807)\n- Windows 11 Version 23H2 (10.0.22631.0 to below 10.0.22631.7652)\n- Windows 11 Version 24H2 (10.0.26100.0 to below 10.0.26100.9711)\n- Windows 11 Version 25H2 (10.0.26200.0 to below 10.0.26200.9711)\n- Windows 11 Version 26H1 (10.0.28000.0 to below 10.0.28000.3231)\n- Windows 11 Version 26H2 (10.0.26300.0 to below 10.0.26300.9711)\n- Windows Server 2012 and Server Core installation (6.2.9200.0 to below 6.2.9200.26434)\n- Windows Server 2012 R2 and Server Core installation (6.3.9600.0 to below 6.3.9600.23470)\n- Windows Server 2016 (10.0.14393.0 to below 10.0.14393.9612)\nNote: one mirror lists Windows 10 22H2 with a 21H2 build range; the MSRC page is authoritative. Windows Server 2025 values differ between mirrors and are unverified.

Fixed in

• Install the October 2026 Microsoft security update for each affected Windows version, reaching at least the build numbers listed above.\n- Windows 10 Version 1809 and Windows Server 2019: KB5126651\n- Windows 11 Version 23H2: KB5126653\n- Windows 10 Version 1607 and Windows Server 2016: KB number unknown; check the MSRC page.

Workaround

Unknown.

Exploitation

• Microsoft: not publicly disclosed, not exploited, exploitability assessment "Exploitation Less Likely".\n- Exploit code maturity: Unproven (E:U).\n- CISA SSVC: Automatable no, Technical Impact total.\n- EPSS about 0.004 (one mirror).\n- No public proof of concept found. CISA KEV status not verified.

Our recommendation

• Patch with the October 2026 cumulative update, starting with Windows 10 1607 and Server 2016 and with terminal servers, shared workstations and systems with many local accounts.\n- Check the support status of Windows 10 1607 and Server 2016 with Microsoft and plan replacement if they are no longer supported.\n- Confirm affected builds and the 1607/2016 KB on the MSRC page and check CISA KEV.\n- Monitor for unusual local privilege escalation on unpatched hosts.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

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

Research sources

• Microsoft Security Update Guide (MSRC) msrc.microsoft.com
• Vulners NVD mirror vulners.com
• Vulners CVElist mirror vulners.com
• Vulners Rapid7 entry (Windows) vulners.com
• Vulners MSCVE mirror vulners.com
• Tenable plugin 365468 www.tenable.com
• SonicWall Microsoft October 2026 coverage www.sonicwall.com
• Vulners Rapid7 entry vulners.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 2 Nov 2026, 03:48.