Microsoft Windows up to Server 2019 Kernel memory corruption

CVSS Meta Temp Score
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Current Exploit Price (≈)
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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$5k-$25k0.00

Summaryinfo

A vulnerability has been found in Microsoft Windows and classified as very critical. Affected by this issue is some unknown functionality of the component Kernel. This manipulation causes an unknown weakness. This vulnerability is handled as CVE-2021-33771. The attack can be initiated remotely. Additionally, an exploit exists. To fix this issue, it is recommended to deploy a patch.

Detailsinfo

A vulnerability was found in Microsoft Windows (Operating System). It has been declared as very critical. Affected by this vulnerability is an unknown part of the component Kernel. The CWE definition for the vulnerability is CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. As an impact it is known to affect confidentiality, integrity, and availability.

The weakness was released 07/13/2021 as confirmed security guidance (Website). It is possible to read the advisory at portal.msrc.microsoft.com. This vulnerability is known as CVE-2021-33771. Technical details are unknown but an exploit is available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 10/29/2025).

It is declared as attacked. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 11/03/2021 with a due date of 11/17/2021:

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 databases at Zero-Day.cz (649) and EUVD (EUVD-2021-20448). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

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Vendor

Name

Version

License

Website

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

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Memory corruption
CWE: CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: Yes

Availability: 🔍
Status: Attacked

EPSS Score: 🔍
EPSS Percentile: 🔍

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

Price Prediction: 🔍
Current Price Estimation: 🔍

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Zero-Day.cz: 🔍

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Patch
Status: 🔍

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

Timelineinfo

05/28/2021 🔍
07/13/2021 +46 days 🔍
07/13/2021 +0 days 🔍
07/14/2021 +0 days 🔍
10/29/2025 +1568 days 🔍

Sourcesinfo

Vendor: microsoft.com
Product: microsoft.com

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

CVE: CVE-2021-33771 (🔍)
GCVE (CVE): GCVE-0-2021-33771
GCVE (VulDB): GCVE-100-178531
EUVD: 🔍
scip Labs: https://www.scip.ch/en/?labs.20161215

Entryinfo

Created: 07/14/2021 08:00
Updated: 10/29/2025 19:25
Changes: 07/14/2021 08:00 (33), 07/14/2021 08:04 (22), 07/17/2021 09:42 (2), 04/21/2024 19:59 (29), 06/26/2024 06:05 (2), 07/26/2024 21:49 (28), 09/15/2024 13:07 (1), 07/29/2025 03:23 (1), 10/29/2025 19:25 (1)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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