What is the CVSS score of CVE-2021-1732?

CVE-2021-1732 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: 90.1%.

Is there a public PoC exploit available for CVE-2021-1732?

Yes, a public proof-of-concept exploit is available for CVE-2021-1732. Prioritise patching immediately. EPSS: 90.1%.

How to fix or mitigate CVE-2021-1732?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. If patching is delayed, consider network segmentation to limit exposure.

Windows 10 1809 CVE-2021-1732

HIGH

Out-of-bounds Write (CWE-787)

2021-02-25 secure@microsoft.com

Buffer Overflow Memory Corruption Microsoft Windows 10 1809 Windows Server 2019 Windows 10 1909 Windows 10 20H2 Windows Server 2004 Windows 10 1803 Windows Server 1909 Windows 10 2004 Windows Server 20H2

7.8

CVSS 3.1 · Vendor: microsoft

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Vulnerability Assessment

Weakness	CWE CWE-787 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V14 - Configuration Dependency management, component inventory MITRE ATT&CK 2 techniques across 2 tactics: Execution, Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	High risk (EPSS 90%). Attributed to the Bitter APT group targeting South Asian government and military organizations. Win32k continues to be the most exploited kernel component in Windows.
Exploit ScenarioDerived	Bitter APT operators deliver malicious documents to government targets. After the document exploit achieves initial code execution, CVE-2021-1732 escalates to SYSTEM privileges for deploying persistent surveillance tools.

Act Now Prioritize within 24-48h. Why: In CISA KEV with patch available.

Exploited in the wild (CISA KEV) Patch available 90.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 26, 2026

Windows Win32k contains an out-of-bounds write vulnerability enabling local privilege escalation to SYSTEM, exploited by the Bitter APT group in February 2021 for targeted espionage operations.

Earlier versions of this analysis (1)

v1 Mar 26, 2026 - 11:19 CVSS 7.8

A Win32k privilege escalation vulnerability allows local users to gain SYSTEM privileges through crafted applications. Exploited in the wild by the Bitter APT group (South Asian nexus) in early 2021.

RemediationAI

Apply Microsoft security update. Deploy Win32k syscall filtering via Windows Defender Exploit Guard ASR rules.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

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

Technical ContextAI · show details

The CWE-787 out-of-bounds write in win32k.sys occurs during processing of specific window message operations. The kernel write primitive enables token manipulation for privilege escalation from any user context to SYSTEM.

Severity by source

Vendor (microsoft) PRIMARY 7.8 HIGH

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

Primary rating from Vendor (microsoft) · only source for this CVE.

CVSS VectorVendor: microsoft

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Added to CISA KEV

Oct 30, 2025 - 19:56 cisa

CISA KEV

PoC Detected

Oct 30, 2025 - 19:56 vuln.today

Public exploit code

Patch released

Oct 30, 2025 - 19:56 nvd

Patch available

CVE Published

Feb 25, 2021 - 23:15 nvd

HIGH 7.8

DescriptionCVE.org

Windows Win32k Elevation of Privilege Vulnerability

Executive ViewAI

Why It Matters

CVE-2021-1732 presents notable security risk, a out-of-bounds write vulnerability rated CVSS 7.8. Exploitation could allow attackers to corrupt memory, crash the application, or potentially execute arbitrary code. This vulnerability is actively exploited in the wild (KEV-listed) and requires immediate remediation. A patch is available and should be applied as part of regular vulnerability management.

Business Impact: Severe

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Enable ASLR and DEP where available; (2) Implement network segmentation; (3) Monitor for exploitation indicators.

Threat Intelligence Overview

Threat Score

9.3/10

Composite threat intelligence

EPSS Score

90.1%

Top 0% exploitable

Threat Intel

1 sources

Exploit

POC

Public exploit code exists

Data Quality

6 sources

Confidence: High

NVD

CVE.org

CISA KEV

EPSS POC (1) THREAT

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 Yes

Public POC Yes

EPSS 90.1%

Patch available Yes

Active threat Yes

Deciding rule

In CISA KEV with patch available

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

Out-of-Cycle

Exploitation· derived

Active

System Exposure· derived

Small

Automatable· derived

Human Impact

Very High

Priority Score

224

Low Medium High Critical

KEV: +50

EPSS: +90

CVSS: +39

PoC: +20

Weaponized: +15

Threat intel: +10

Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Memory Corruption HIGH

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.