Microsoft Windows up to Server 2025 Hyper-V heap-based overflow

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.
6.9	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Microsoft Windows. It has been declared as critical. The affected element is an unknown function of the component Hyper-V. Executing a manipulation can lead to heap-based overflow. The identification of this vulnerability is CVE-2026-21248. The attack can only be executed locally. Furthermore, there is an exploit available. A patch should be applied to remediate this issue.

Detailsinfo

A vulnerability was found in Microsoft Windows. It has been declared as critical. This vulnerability affects some unknown processing of the component Hyper-V. The manipulation with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Heap-based buffer overflow in Windows Hyper-V allows an authorized attacker to execute code locally.

The weakness was shared 02/10/2026 as confirmed security update guide (Website). The advisory is available at msrc.microsoft.com. This vulnerability was named CVE-2026-21248. The exploitation appears to be easy. Local access is required to approach this attack. Technical details are unknown but a public exploit is available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 05/13/2026).

It is possible to download the exploit at exploit-db.com. It is declared as proof-of-concept.

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 Exploit-DB (52537). If you want to get best quality of vulnerability data, you may have to visit VulDB.

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: 7.5
VulDB Meta Temp Score: 6.9

VulDB Base Score: 7.8
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 7.3
Vendor Vector (Microsoft): 🔒

CNA Base Score: 7.3
CNA Vector (Microsoft): 🔒

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Heap-based overflow
CWE: CWE-122 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Access: Public
Status: Proof-of-Concept
Download: 🔒

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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

Exploit-DB: 🔒

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Patch
Status: 🔍

Reaction Time: 🔒
0-Day Time: 🔒
Exposure Time: 🔒

Timelineinfo

02/10/2026 VulDB entry created
02/10/2026 +0 days Advisory disclosed
02/10/2026 +0 days Countermeasure disclosed
05/13/2026 +91 days VulDB entry last update