CVE-2026-88234: Windows iSCSI Remote Code Execution Vulnerability
CVE-2026-88234 is a remote code execution vulnerability in Windows iSCSI, rated Important by Microsoft, with a CVSS 3.1 base score of 9.8 (Critical). An attacker can exploit it remotely over the network, without any privileges and without user interaction. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. Microsoft released the fix on 10 November 2026 in the November 2026 Patch Tuesday, delivered through 5 security updates (KB5131291, KB5131085, KB5131090, KB5131080 and more). It affects 8 products in 2 product families (ESU, Windows).
Key facts
- CVE ID
- CVE-2026-88234
- Severity
- Critical CVSS 9.8
- Microsoft severity
- Important
- Impact
- Remote Code Execution
- Exploited in the wild
- No
- Publicly disclosed
- No
- Exploitation likelihood
- Less Likely
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- November 2026 Patch Tuesday
- Product families
- ESU, Windows
From the November 2026 Patch Tuesday briefing
Windows iSCSI code execution
This critical iSCSI remote code execution flaw affects Windows and ESU, bringing affected storage-connected systems into the network-critical workload. Exploitation requires neither sign-in nor user action. Microsoft rates exploitation less likely. The weakness is CWE-763, release of an invalid pointer or reference. CVSS: 9.8, vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C.
From the briefing, written by an AI model from PatchaPalooza's data.
CVSS score and vector
Microsoft scores CVE-2026-88234 at 9.8 (temporal 8.5) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality impact | High |
| Integrity impact | High |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Description
Release of invalid pointer or reference in Windows iSCSI allows an unauthorized attacker to execute code over a network.
Frequently asked questions (Microsoft)
How could an attacker exploit this vulnerability?
Successful exploitation of this vulnerability could allow an attacker the ability to gain remote code execution via an in-network attacker calling arbitrary endpoints.
Affected products (8)
ESU
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Windows Server 2016 | KB5131291 | Security Update | 10.0.14393.9688 | Yes |
| Windows Server 2016 (Server Core installation) | KB5131291 | Security Update | 10.0.14393.9688 | Yes |
Windows
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Windows Server 2019 | KB5131085 | Security Update | 10.0.17763.9487 | Yes |
| Windows Server 2019 (Server Core installation) | KB5131085 | Security Update | 10.0.17763.9487 | Yes |
| Windows Server 2022 | KB5131090 | Security Update | 10.0.20348.5870 | Yes |
| Windows Server 2022 (Server Core installation) | KB5131090 | Security Update | 10.0.20348.5870 | Yes |
| Windows Server 2025 | KB5131080 KB5131077 | Security Update Security Update | 10.0.26100.33822 10.0.26100.33730 | Yes No |
| Windows Server 2025 (Server Core installation) | KB5131080 KB5131077 | Security Update Security Update | 10.0.26100.33822 10.0.26100.33730 | Yes No |
Security updates (5)
Acknowledgments
- Seung Chan Kim
- Anemone
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. |