CVE-2026-33837: Windows TCP/IP Local Elevation of Privilege Vulnerability

CVE-2026-33837 is an elevation of privilege vulnerability in Windows TCP/IP Local, rated Important by Microsoft, with a CVSS 3.1 base score of 7.8 (High). An attacker can exploit it by an attacker with local access, with low privileges and without user interaction. Microsoft has not reported exploitation in the wild and rates exploitation as more likely. The EPSS model estimates a 1.84% probability of exploitation activity in the next 30 days, higher than 79% of all scored vulnerabilities. Microsoft released the fix on 12 May 2026 in the May 2026 Patch Tuesday, delivered through 16 security updates (KB5087538, KB5087545, KB5087424, KB5087544 and more). It affects 31 products in 2 product families (Windows, ESU).

Key facts

CVE ID: CVE-2026-33837
Severity: High CVSS 7.8
Microsoft severity: Important
Impact: Elevation of Privilege
Exploited in the wild: No
Publicly disclosed: No
Exploitation likelihood: More Likely
Weakness: CWE-122
EPSS: 1.84% (percentile 79%)
CISA KEV: Not listed
Released: 12 May 2026
Last updated: 12 May 2026
Patch Tuesday: May 2026 Patch Tuesday
Product families: Windows, ESU

CVSS score and vector

Microsoft scores CVE-2026-33837 at 7.8 (temporal 6.8) using CVSS 3.1. Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Metric	Value
Attack vector	Local
Attack complexity	Low
Privileges required	Low
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

Heap-based buffer overflow in Windows TCP/IP allows an authorized attacker to elevate privileges locally.

Frequently asked questions (Microsoft)

How could an attacker exploit this vulnerability?

An attacker could exploit this vulnerability locally by running code with limited privileges and then interacting with the tcpip.sys kernel driver to gain elevated (kernel-level) privileges on the system.

Affected products (31)

Windows

Product	Security update	Type	Fixed build	Restart
Windows 10 Version 1809 for 32-bit Systems	KB5087538	Security Update	10.0.17763.8755	Yes
Windows 10 Version 1809 for x64-based Systems	KB5087538	Security Update	10.0.17763.8755	Yes
Windows Server 2019	KB5087538	Security Update	10.0.17763.8755	Yes
Windows Server 2019 (Server Core installation)	KB5087538	Security Update	10.0.17763.8755	Yes
Windows Server 2022	KB5087545 KB5087424	Security Update Security Hotpatch Update	10.0.20348.5139 10.0.20348.5074	Yes Yes
Windows Server 2022 (Server Core installation)	KB5087545 KB5087424	Security Update Security Hotpatch Update	10.0.20348.5139 10.0.20348.5074	Yes Yes
Windows 10 Version 21H2 for 32-bit Systems	KB5087544	Security Update	10.0.19044.7291	Yes
Windows 10 Version 21H2 for ARM64-based Systems	KB5087544	Security Update	10.0.19044.7291	Yes
Windows 10 Version 21H2 for x64-based Systems	KB5087544	Security Update	10.0.19044.7291	Yes
Windows Server 2025 (Server Core installation)	KB5087539 KB5087423	Security Update Security Hotpatch Update	10.0.26100.32860 10.0.26100.32772	Yes Yes
Windows 11 Version 25H2 for ARM64-based Systems	KB5089549 KB5089466	Security Update Security Hotpatch Update	10.0.26200.8457 10.0.26200.8390	Yes Yes
Windows 11 Version 25H2 for x64-based Systems	KB5089549 KB5089466	Security Update Security Hotpatch Update	10.0.26200.8457 10.0.26200.8390	Yes Yes
Windows 11 Version 23H2 for ARM64-based Systems	KB5087420	Security Update	10.0.22631.7079	Yes
Windows 11 Version 23H2 for x64-based Systems	KB5093998	Security Update	10.0.22631.7219	Yes
Windows Server 2022, 23H2 Edition (Server Core installation)	KB5087541	Security Update	10.0.25398.2330	Yes
Windows 11 Version 24H2 for ARM64-based Systems
Windows 11 Version 24H2 for x64-based Systems
Windows Server 2025	KB5087539 KB5087423	Security Update Security Hotpatch Update	10.0.26100.32860 10.0.26100.32772	Yes Yes
Windows 11 version 26H1 for x64-based Systems	KB5089548	Security Update	10.0.28000.2113	Yes
Windows 11 Version 26H1 for ARM64-based Systems	KB5089548	Security Update	10.0.28000.2113	Yes
Windows 10 Version 1607 for 32-bit Systems	KB5087537	Security Update	10.0.14393.9140	Yes
Windows 10 Version 1607 for x64-based Systems	KB5087537	Security Update	10.0.14393.9140	Yes
Windows Server 2016	KB5087537	Security Update	10.0.14393.9140	Yes
Windows Server 2016 (Server Core installation)	KB5087537	Security Update	10.0.14393.9140	Yes

ESU

Product	Security update	Type	Fixed build	Restart
Windows 10 Version 22H2 for x64-based Systems	KB5094127	Security Update	10.0.19045.7417	Yes
Windows 10 Version 22H2 for ARM64-based Systems	KB5094127	Security Update	10.0.19045.7417	Yes
Windows 10 Version 22H2 for 32-bit Systems	KB5094127	Security Update	10.0.19045.7417	Yes
Windows Server 2012	KB5087470	Monthly Rollup	6.2.9200.26079	Yes
Windows Server 2012 (Server Core installation)	KB5087470	Monthly Rollup	6.2.9200.26079	Yes
Windows Server 2012 R2	KB5087471	Monthly Rollup	6.3.9600.23181	Yes
Windows Server 2012 R2 (Server Core installation)	KB5087471	Monthly Rollup	6.3.9600.23181	Yes

Security updates (16)

KB5087538 (Security Update)
KB5087545 (Security Update)
KB5087424 (Security Hotpatch Update)
KB5087544 (Security Update)
KB5094127 (Security Update)
KB5087539 (Security Update)
KB5087423 (Security Hotpatch Update)
KB5089549 (Security Update)
KB5089466 (Security Hotpatch Update)
KB5087420 (Security Update)
KB5093998 (Security Update)
KB5087541 (Security Update)
KB5089548 (Security Update)
KB5087537 (Security Update)
KB5087470 (Monthly Rollup)
KB5087471 (Monthly Rollup)

NIST NVD data

NVD status: Analyzed
NVD CVSS: 7.8 (HIGH)
NVD weakness: CWE-122
Published to NVD: 12 May 2026
NVD last modified: 14 May 2026

Affected configurations (CPE)

Product	Vulnerable versions
windows 10 1607 (x64)	before 10.0.14393.9140
windows 10 1607 (x86)	before 10.0.14393.9140
windows 10 1809 (x64)	before 10.0.17763.8755
windows 10 1809 (x86)	before 10.0.17763.8755
windows 10 21h2 (arm64)	before 10.0.19044.7291
windows 10 21h2 (x64)	before 10.0.19044.7291
windows 10 21h2 (x86)	before 10.0.19044.7291
windows 10 22h2 (arm64)	before 10.0.19045.7291
windows 10 22h2 (x64)	before 10.0.19045.7291
windows 10 22h2 (x86)	before 10.0.19045.7291
windows 11 23h2 (arm64)	before 10.0.22631.7079
windows 11 23h2 (x64)	before 10.0.22631.7079
windows 11 24h2 (arm64)	before 10.0.26100.8390
windows 11 24h2 (x64)	before 10.0.26100.8390
windows 11 25h2 (arm64)	before 10.0.26200.8390
windows 11 25h2 (x64)	before 10.0.26200.8390
windows 11 26h1 (arm64)	before 10.0.28000.2113
windows 11 26h1 (x64)	before 10.0.28000.2113
windows server 2012	all listed versions
windows server 2012 r2	all listed versions
windows server 2016	before 10.0.14393.9140
windows server 2019	before 10.0.17763.8755
windows server 2022	before 10.0.20348.5074
windows server 2022 23h2	before 10.0.25398.2330
windows server 2025	before 10.0.26100.32772

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33837 (Vendor Advisory)

Acknowledgments

Revision history

Version	Date	Description
1.0	12 May 2026	Information published.