CVE-2025-21333: Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability
CVE-2025-21333 is an elevation of privilege vulnerability in Windows Hyper-V NT Kernel Integration VSP, rated Important by Microsoft, with a CVSS 3.1 base score of 7.8 (High). An attacker can exploit it by an attacker with local access, with low privileges and without user interaction. Microsoft reports that it has been exploited in the wild. CISA added it to the Known Exploited Vulnerabilities catalog on 14 January 2025, with a remediation deadline of 4 February 2025 for US federal agencies. The EPSS model estimates a 10.07% probability of exploitation activity in the next 30 days, higher than 96% of all scored vulnerabilities. Microsoft released the fix on 14 January 2025 in the January 2025 Patch Tuesday, delivered through 4 security updates (KB5049981, KB5050021, KB5050009, KB5049984). It affects 11 products in 2 product families (Windows, ESU).
Key facts
- CVE ID
- CVE-2025-21333
- Severity
- High CVSS 7.8
- Microsoft severity
- Important
- Impact
- Elevation of Privilege
- Exploited in the wild
- Yes
- Publicly disclosed
- No
- Exploitation likelihood
- Detected
- Weakness
- CWE-122
- EPSS
- 10.07% (percentile 96%)
- CISA KEV
- Listed , due
- Released
- Last updated
- Patch Tuesday
- January 2025 Patch Tuesday
- Product families
- Windows, ESU
CVSS score and vector
Microsoft scores CVE-2025-21333 at 7.8 (temporal 6.8) using CVSS 3.1. Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Local |
| Attack complexity | Low |
| Privileges required | Low |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality impact | High |
| Integrity impact | High |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Frequently asked questions (Microsoft)
What privileges could be gained by an attacker who successfully exploited this vulnerability?
An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.
Does this vulnerability exist in the Hyper-V server?
No, the Hyper-V NT Kernel Integration Virtual Service Provider (VSP) is a component used for communications between the host OS and container-type VMs, such as Windows Sandbox and Microsoft Defender Application Guard (MDAG). It is not in a traditional Hyper-V VM environment. Whereas traditional Hyper-V VMs have a strong boundary between the host and the guest for isolation purposes, container-type VMs like MDAG simulate that they are running on the host. The Hyper-V NT Kernel Integration VSP driver has functionality that enables this simulation.
Microsoft strongly recommends updating to the latest version of Windows to be protected against this vulnerability.
Is this a guest to host type of vulnerability?
No, this is a local elevation of privilege, not any type of guest to host escape.
Affected products (11)
Windows
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Windows 10 Version 21H2 for x64-based Systems | KB5049981 | Security Update | 10.0.19044.5371 | Yes |
| Windows Server 2025 (Server Core installation) | KB5050009 | Security Update | 10.0.26100.2894 | Yes |
| Windows 11 Version 23H2 for ARM64-based Systems | ||||
| Windows 11 Version 23H2 for x64-based Systems | ||||
| Windows Server 2022, 23H2 Edition (Server Core installation) | KB5049984 | Security Update | 10.0.25398.1369 | Yes |
| Windows 11 Version 24H2 for ARM64-based Systems | KB5050009 | Security Update | 10.0.26100.2894 | Yes |
| Windows 11 Version 24H2 for x64-based Systems | KB5050009 | Security Update | 10.0.26100.2894 | Yes |
| Windows Server 2025 | KB5050009 | Security Update | 10.0.26100.2894 | Yes |
ESU
Security updates (4)
Exploitation and detection
CISA Known Exploited Vulnerabilities
- Date added
- Federal due date
- Ransomware use
- Unknown
- Required action
- Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
VulnCheck KEV
- Date added
- Ransomware use
- Unknown
- Independent sources
- 4
- · api.msrc.microsoft.com
- · msrc.microsoft.com
- · cisa.gov
- · securelist.com
- · kelacyber.com
- · loginsoft.com
- · ussc.ru
Public exploits (8)
- uname1able/CVE-2025-21333 · added
- nu1lptr0/CVE-2025-21333 · added
- pradip022/CVE-2025-21333-POC · added
- B1ack4sh/Blackash-CVE-2025-21333 · added
- 160102/CVE-2025-21333-POC · added
- SerabiLem/CVE-2025-21333-POC · added
- Mukesh-blend/CVE-2025-21333-POC · added
- MrAle98/CVE-2025-21333-POC · added
Detection and weaponization
Weaponization maturity: Exploit.
Proof-of-concept repositories (4)
NIST NVD data
- NVD status
- Analyzed
- NVD CVSS
- 7.8 (HIGH)
- NVD weakness
- CWE-122
- Published to NVD
- NVD last modified
Affected configurations (CPE)
| Product | Vulnerable versions |
|---|---|
| windows 10 21h2 (x64) | before 10.0.19044.5371 |
| windows 10 22h2 (x64) | before 10.0.19045.5371 |
| windows 11 22h2 | before 10.0.22621.4751 |
| windows 11 23h2 | before 10.0.22631.4751 |
| windows 11 24h2 | before 10.0.26100.2894 |
| windows server 2022 23h2 (x64) | before 10.0.25398.1369 |
| windows server 2025 (x64) | before 10.0.26100.2894 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21333 (Patch, Vendor Advisory)
- https://www.exploit-db.com/exploits/52436 (Exploit, Third Party Advisory, VDB Entry)
- https://www.vicarius.io/vsociety/posts/cve-2025-21333-elevated-privilege-exposure-in-windows-hyper-v-by-microsoft-detection-script (Mitigation, Third Party Advisory)
- https://www.vicarius.io/vsociety/posts/cve-2025-21333-elevated-privilege-exposure-in-windows-hyper-v-by-microsoft-mitigation-script (Mitigation, Third Party Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-21333 (US Government Resource)
Acknowledgments
- Anonymous
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. | |
| 1.1 | Added FAQ information. This is an informational change only. |