# Microsoft Windows Kernel Exposed IOCTL with Insufficient Access Control · pwn.watch

> Microsoft Windows Kernel contains an exposed IOCTL with insufficient access control vulnerability within the IOCTL (input and output control) dispatcher in appid.sys that allows a local attacker to achieve privilege escalation. Added to the CISA KEV catalog on 2024-03-04. CISA lists known use in ransomware campaigns.

Page: https://pwn.watch/i/microsoft-windows-cve-2024-21338 · generated 2026-10-22T20:45:43.249Z

## Status
- Severity: high · status: closed · patch: patched
- Product: Microsoft Windows
- Started: 2024-02-13 · closed: 2024-03-04
- CVEs: CVE-2024-21338
- Affected: See vendor advisory (versions are not listed in the KEV record)
- Fixed in: See vendor advisory linked in sources

## Follow this incident
- RSS (one item per update): https://pwn.watch/i/microsoft-windows-cve-2024-21338/feed.xml
- JSON Feed: https://pwn.watch/i/microsoft-windows-cve-2024-21338/feed.json
- Full data (timeline, sources, posts, agentBrief): https://pwn.watch/i/microsoft-windows-cve-2024-21338.json
- This file: https://pwn.watch/i/microsoft-windows-cve-2024-21338/llms.txt

## Updates (newest first)
- 2024-03-04: CISA added CVE-2024-21338 to the KEV catalog (federal deadline 2024-03-25) (https://www.cisa.gov/known-exploited-vulnerabilities-catalog)
- 2024-02-13: CVE-2024-21338 published (https://nvd.nist.gov/vuln/detail/CVE-2024-21338)

## Fix brief
# Security brief: Microsoft Windows Kernel Exposed IOCTL with Insufficient Access Control

Source: https://pwn.watch/i/microsoft-windows-cve-2024-21338 · status: closed (closed Mar 4, 2024) · severity: high · updated Mar 4, 2024

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

## What it is
Microsoft Windows Kernel contains an exposed IOCTL with insufficient access control vulnerability within the IOCTL (input and output control) dispatcher in appid.sys that allows a local attacker to achieve privilege escalation. Added to the CISA KEV catalog on 2024-03-04. CISA lists known use in ransomware campaigns.

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

- Product: Microsoft Windows
- CVE / advisory ids: CVE-2024-21338

## Affected versions
- See vendor advisory (versions are not listed in the KEV record)

## 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
- Mar 4, 2024: CISA added CVE-2024-21338 to the KEV catalog (federal deadline 2024-03-25)
- Feb 13, 2024: CVE-2024-21338 published

## Advisories
- [Microsoft advisory: CVE-2024-21338](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-21338) (Microsoft)
- [NVD: CVE-2024-21338](https://nvd.nist.gov/vuln/detail/CVE-2024-21338) (NVD)
- [CISA Known Exploited Vulnerabilities Catalog](https://www.cisa.gov/known-exploited-vulnerabilities-catalog) (CISA)

## Caveats
Derived from the CISA KEV JSON feed (catalogVersion 2026.10.21); CVSS from the CVE record (cveawg.mitre.org). startedAt is the CVE publication date when it fell in 2024 before the KEV listing, else the KEV dateAdded; exploitation may have begun earlier. closedAt is the KEV listing date (a fix or mitigation was available then unless noted).

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Machine-readable: https://pwn.watch/i/microsoft-windows-cve-2024-21338.json · all incidents: https://pwn.watch/incidents.json. Verify against the vendor advisory before changing production systems.