VDB-184265 · CVE-2021-40449 · GCVE-0-2021-40449

Microsoft Windows up to Server 2022 Win32k use after free

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.8	$0-$5k	0.00

Summaryinfo

A vulnerability marked as very critical has been reported in Microsoft Windows. This issue affects some unknown processing of the component Win32k. The manipulation leads to an unknown weakness. This vulnerability is referenced as CVE-2021-40449. Remote exploitation of the attack is possible. Furthermore, an exploit is available. It is suggested to install a patch to address this issue.

Detailsinfo

A vulnerability was found in Microsoft Windows (Operating System). It has been rated as very critical. This issue affects an unknown code of the component Win32k. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability.

The weakness was published 10/12/2021 as confirmed security guidance (Website). The advisory is shared at portal.msrc.microsoft.com. The identification of this vulnerability is CVE-2021-40449. Technical details are unknown but a public exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/30/2025).

A public exploit has been developed by Gal Kristal in C and been published 4 weeks after the advisory. The exploit is available at github.com. It is declared as attacked. We expect the 0-day to have been worth approximately $100k and more. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 11/17/2021 with a due date of 12/01/2021:

Apply updates per vendor instructions.

Applying a patch is able to eliminate this problem. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at Zero-Day.cz (671). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

Operating System

Vendor

Microsoft

Name

Windows

Version

License

commercial

Website

Vendor: https://www.microsoft.com/
Product: https://www.microsoft.com/en-us/windows

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.1
VulDB Meta Temp Score: 7.8

VulDB Base Score: 8.8
VulDB Temp Score: 8.4
VulDB Vector: 🔍
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 7.8
Vendor Vector (Microsoft): 🔍

NVD Base Score: 7.8
NVD Vector: 🔍

CNA Base Score: 7.8
CNA Vector (Microsoft): 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: Yes

Availability: 🔍
Access: Public
Status: Attacked
Author: Gal Kristal
Programming Language: 🔍
Download: 🔍

EPSS Score: 🔍
EPSS Percentile: 🔍

KEV Added: 🔍
KEV Due: 🔍
KEV Remediation: 🔍
KEV Ransomware: 🔍
KEV Notice: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Zero-Day.cz: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍
Exploit Delay Time: 🔍

Timelineinfo

09/02/2021 🔍
10/12/2021 +40 days 🔍
10/12/2021 +0 days 🔍
10/12/2021 +0 days 🔍
11/07/2021 +25 days 🔍
10/30/2025 +1453 days 🔍

Sourcesinfo

Vendor: microsoft.com
Product: microsoft.com

Advisory: portal.msrc.microsoft.com
Status: Confirmed

CVE: CVE-2021-40449 (🔍)
GCVE (CVE): GCVE-0-2021-40449
GCVE (VulDB): GCVE-100-184265
scip Labs: https://www.scip.ch/en/?labs.20161215

Entryinfo

Created: 10/12/2021 21:25
Updated: 10/30/2025 21:41
Changes: 10/12/2021 21:25 (17), 10/12/2021 21:26 (17), 10/12/2021 21:29 (21), 10/15/2021 10:14 (2), 11/11/2021 19:58 (9), 04/22/2024 08:06 (28), 06/23/2024 22:54 (2), 07/25/2024 01:11 (28), 09/16/2024 14:18 (1), 10/30/2025 21:41 (1)
Complete: 🔍
Committer: misc
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.