# Microsoft Windows: 3 exploited vulnerabilities (CVE-2025-21333, CVE-2025-21334, CVE-2025-21335) · pwn.watch

> CVE-2025-21333: Microsoft Windows Hyper-V NT Kernel Integration VSP contains a heap-based buffer overflow vulnerability that allows a local attacker to gain SYSTEM privileges. CVE-2025-21334: Microsoft Windows Hyper-V NT Kernel Integration VSP contains a use-after-free vulnerability that allows a local attacker to gain SYSTEM privileges. CVE-2025-21335: Microsoft Windows Hyper-V NT Kernel Integration VSP contains a use-after-free vulnerability that allows a local attacker to gain SYSTEM privileges. Added to CISA KEV on 2025-01-14.

Page: https://pwn.watch/i/microsoft-windows-cve-2025-21333 · generated 2026-10-23T04:59:28.006Z

## Status
- Severity: high · status: closed · patch: patched
- Product: Microsoft Windows
- Started: 2025-01-14 · closed: 2025-01-14
- CVEs: CVE-2025-21333, CVE-2025-21334, CVE-2025-21335
- Affected: See vendor advisory / CISA notes (versions not always listed in KEV feed)
- Fixed in: See vendor advisory linked in sources

## Follow this incident
- RSS (one item per update): https://pwn.watch/i/microsoft-windows-cve-2025-21333/feed.xml
- JSON Feed: https://pwn.watch/i/microsoft-windows-cve-2025-21333/feed.json
- Full data (timeline, sources, posts, agentBrief): https://pwn.watch/i/microsoft-windows-cve-2025-21333.json
- This file: https://pwn.watch/i/microsoft-windows-cve-2025-21333/llms.txt

## Updates (newest first)
- 2025-01-14: CISA added CVE-2025-21333 to the KEV catalog (due 2025-02-04).
- 2025-01-14: CISA added CVE-2025-21334 to the KEV catalog (due 2025-02-04).
- 2025-01-14: CISA added CVE-2025-21335 to the KEV catalog (due 2025-02-04).

## Fix brief
# Security brief: Microsoft Windows: 3 exploited vulnerabilities (CVE-2025-21333, CVE-2025-21334, CVE-2025-21335)

Source: https://pwn.watch/i/microsoft-windows-cve-2025-21333 · status: closed (closed Jan 14, 2025) · severity: high · updated Jan 14, 2025

## Patch status
**PATCHED: fixed releases exist. Upgrade to a fixed version.**

## What it is
CVE-2025-21333: Microsoft Windows Hyper-V NT Kernel Integration VSP contains a heap-based buffer overflow vulnerability that allows a local attacker to gain SYSTEM privileges. CVE-2025-21334: Microsoft Windows Hyper-V NT Kernel Integration VSP contains a use-after-free vulnerability that allows a local attacker to gain SYSTEM privileges. CVE-2025-21335: Microsoft Windows Hyper-V NT Kernel Integration VSP contains a use-after-free vulnerability that allows a local attacker to gain SYSTEM privileges. Added to CISA KEV on 2025-01-14.

Severity detail: CVSS 7.8 (CNA, v3.1); actively exploited (CISA KEV)

- Product: Microsoft Windows
- CVE / advisory ids: CVE-2025-21333, CVE-2025-21334, CVE-2025-21335

## Affected versions
- See vendor advisory / CISA notes (versions not always listed in KEV feed)

## Check whether you're affected
No generic command applies (the product is a hosted service, appliance or desktop app). Check the installed version in its admin UI / About screen and compare with the versions above.

## Fix
Upgrade to one of these fixed versions (or later on the same branch):
- See vendor advisory linked in sources

After upgrading, re-run the checks above and redeploy/restart the affected services.

## Latest updates
- Jan 14, 2025: CISA added CVE-2025-21333 to the KEV catalog (due 2025-02-04).
- Jan 14, 2025: CISA added CVE-2025-21334 to the KEV catalog (due 2025-02-04).
- Jan 14, 2025: CISA added CVE-2025-21335 to the KEV catalog (due 2025-02-04).

## Advisories
- [Microsoft advisory: Microsoft Windows](https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-21333) (Microsoft)
- [Microsoft advisory: Microsoft Windows](https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-21334) (Microsoft)
- [Microsoft advisory: Microsoft Windows](https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-21335) (Microsoft)
- [NVD: CVE-2025-21333](https://nvd.nist.gov/vuln/detail/CVE-2025-21333) (NVD)
- [NVD: CVE-2025-21334](https://nvd.nist.gov/vuln/detail/CVE-2025-21334) (NVD)
- [NVD: CVE-2025-21335](https://nvd.nist.gov/vuln/detail/CVE-2025-21335) (NVD)
- [CISA Known Exploited Vulnerabilities Catalog](https://www.cisa.gov/known-exploited-vulnerabilities-catalog) (CISA)

## Caveats
Derived from CISA KEV JSON feed catalogVersion 2026.10.21. CVSS from the CVE record (cvelistV5). Exact affected/fixed version strings are not always in the KEV record; verify against the vendor advisory URL. startedAt uses dateAdded (exploitation may have begun earlier; many entries are older CVEs newly confirmed as exploited in 2025).

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Machine-readable: https://pwn.watch/i/microsoft-windows-cve-2025-21333.json · all incidents: https://pwn.watch/incidents.json. Verify against the vendor advisory before changing production systems.