What is the CVSS score of CVE-2026-21250?

CVE-2026-21250 has a CVSS 3.1 base score of 7.8 (High). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.0%.

Is there a public PoC exploit available for CVE-2026-21250?

Yes, a public proof-of-concept exploit is available for CVE-2026-21250. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-21250?

Within 24 hours: Inventory all Windows servers running HTTP.sys and assess exposure in production environments; begin daily monitoring for exploitation attempts. Within 7 days: Implement network segmentation to restrict HTTP.sys service access and limit lateral movement; enforce strict access controls on authenticated accounts. Within 30 days: Deploy compensating controls listed below; establish vendor contact for patch notification; conduct security awareness training on credential protection.

Windows CVE-2026-21250

HIGH

Untrusted Pointer Dereference (CWE-822)

2026-02-10 secure@microsoft.com

Windows Microsoft Windows 11 24h2 Windows 11 25h2 Windows Server 2022 23h2 Windows Server 2025

7.8

CVSS 3.1 · NVD

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Authenticate as low-privileged local user
Exploit

Craft malicious HTTP request to HTTP.sys
Execution

Trigger untrusted pointer dereference
Impact

Execute arbitrary code with SYSTEM privileges

Vulnerability Assessment

Weakness	CWE CWE-822 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Untrusted pointer prevention
Exploitation Conditions	Local user account required on Windows system with HTTP.sys service running. Attacker must be authenticated with PR:L privileges to interact with HTTP.sys kernel driver directly or via vulnerable HTTP service handling.
Impact	CVSS 7.8 (HIGH). Attack vector: Local. Complexity: Low. Privileges required: Low. User interaction: None. Exploitable via local access.
Exploit ScenarioDerived	An attacker could exploit this vulnerability to compromise the affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Windows HTTP.sys contains an unsafe pointer dereference vulnerability that enables authenticated local attackers to escalate privileges on affected systems including Windows 11, Windows Server 2025, and related versions. An attacker with local user access can exploit this flaw to gain system-level privileges with high confidence in successful exploitation. No patch is currently available for this vulnerability.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 22:02 CVSS 7.8

Untrusted pointer dereference in Windows HTTP.sys allows an authorized attacker to elevate privileges locally. [CVSS 7.8 HIGH]

RemediationAI

Monitor vendor advisories for a patch.

Affected Packages

microsoft windows_11_version_24h2_10_0_26100_7840 fix: Windows 11 Version 24H2 for ARM64-based Systems 10.0.26100.7840, Windows 11 Version 24H2 for x64-based Systems 10.0.26100.7840

microsoft windows_11_version_25h2_10_0_26200_7840 fix: Windows 11 Version 25H2 for ARM64-based Systems 10.0.26200.7840, Windows 11 Version 25H2 for x64-based Systems 10.0.26200.7840

microsoft windows_11_version_26h1_10_0_28000_1575 fix: Windows 11 Version 26H1 for ARM64-based Systems 10.0.28000.1575, Windows 11 version 26H1 for x64-based Systems 10.0.28000.1575

microsoft windows_server_2022_23h2_edition_10_0_25398_2149 fix: Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2149

microsoft windows_server_2025_10_0_26100_32370 fix: Windows Server 2025 10.0.26100.32370, Windows Server 2025 (Server Core installation) 10.0.26100.32370

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 5 packages in microsoft

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Affects Windows 11 24H2. Untrusted pointer dereference in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.8 HIGH

AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionCVE.org

Untrusted pointer dereference in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.

Executive ViewAI

Why It Matters

A high-severity vulnerability in Windows HTTP.sys enables authenticated attackers to gain elevated system privileges on affected servers. This poses a critical risk to any organization running Windows-based web infrastructure, as compromise could lead to complete system control and lateral movement across the network.

Business Impact: High

Compensating Controls

Implement the following interim mitigations: (1) Restrict network access to HTTP.sys services using Windows Firewall and network segmentation; (2) Enforce multi-factor authentication (MFA) on all administrative and service accounts to reduce authorized attacker risk; (3) Monitor and log all privilege escalation attempts through Windows Event Viewer; (4) Disable HTTP.sys features not actively required for business operations; (5) Deploy endpoint detection and response (EDR) solutions with escalation detection; (6) Isolate affected systems on separate network segments from critical assets. Continue monitoring vendor advisories daily for patch availability.

Threat Intelligence Overview

EPSS Score

0.0%

Top 94% exploitable

Exploit

POC

Public exploit code exists

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

Exploit-DB

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Small

Automatable· derived

Human Impact

High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +39

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Affected Products (CPE)CVE.org

cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*

cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*

cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*

cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*

cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*

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References

Advisories & patches

ADVISORY https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21250 ADVISORY https://vuldb.com/vuln/345276

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GitHub PoC

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