Windows iSCSI: Remote Code Execution through integer overflow

Summary

An integer overflow or wraparound (CWE-190) in the Windows iSCSI component allows code execution over the network. An unauthorized attacker can exploit this, but the CVSS vector requires user interaction (UI:R). Systems that act as an iSCSI initiator or target are relevant, and the affected versions include Windows 10 Version 1607 and Windows Server 2016.

Affected

• Windows 10 Version 1607: 10.0.14393.0 to before 10.0.14393.9512
• Windows 10 Version 1809: 10.0.17763.0 to before 10.0.17763.9245
• Windows 10 Version 21H2: 10.0.19044.0 to before 10.0.19044.7725
• Windows 10 Version 22H2: 10.0.19045.0 to before 10.0.19045.7725
• 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
• Windows Server 2012 (including Server Core): 6.2.9200.0 to before 6.2.9200.26349
• Windows Server 2012 R2 (including Server Core): 6.3.9600.0 to before 6.3.9600.23398
• Windows Server 2016 (including Server Core): 10.0.14393.0 to before 10.0.14393.9512

Fixed in

• Install the Microsoft security update that brings the build to at least the fixed version listed for each affected product, for example 10.0.14393.9512 for Windows 10 Version 1607 and Windows Server 2016.
• KB numbers for the Windows 10 Version 1607 and Windows Server 2016 build are unknown; confirm them on the MSRC page.

Workaround

• Unknown from Microsoft's data in this review.
• A third-party aggregator suggests disabling the iSCSI initiator or target services, or blocking TCP port 3260, if patching cannot be done immediately. This has not been verified against Microsoft's advisory and disabling iSCSI breaks systems that depend on it.

Exploitation

• CISA SSVC assessment: exploitation none, not automatable, total technical impact.
• Not listed in CISA's KEV catalog; no confirmed exploitation known.
• No public proof of concept found.
• EPSS is low (about 0.7 %, snapshot).

Our recommendation

• Inventory systems with the iSCSI initiator or target role and their Windows builds.
• Patch Windows Server 2016 and Windows 10 Version 1607 systems to build 14393.9512 or later, and verify the fixed builds on the MSRC page.
• Block TCP port 3260 at the perimeter and limit it to dedicated storage networks.
• Check whether Windows 10 Version 1607 is still supported on your devices and plan an upgrade if it is not.

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: CVE-2026-69521 msrc.microsoft.com
• Microsoft Security Update Guide (en-US): CVE-2026-69521 msrc.microsoft.com
• OpenCVE: CVE-2026-69521 app.opencve.io
• Vulners NVD: CVE-2026-69521 vulners.com
• Vulners MSCVE: MS:CVE-2026-69521 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 31 Oct 2026, 19:05.