---
id: "CVE-2026-33824"
kind: "vulnerability"
aliases: ["CVE-2026-33824"]
title: "Double free in Windows IKE Extension allows an unauthorized attacker to execute code over a network"
severity: "critical"
cvss: 9.8
epss: null
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Microsoft Internet Key Exchange (IKE) Service Extensions", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "Windows IKE Service Extensions (IKEEXT)", "fixed": ["10.0.14393.9060", "10.0.17763.8644", "10.0.19044.7184", "10.0.19045.7184", "10.0.22631.6936", "10.0.26100.8246", "10.0.26200.8246", "10.0.28000.1836"], "affected": "all supported Windows 10/11/Server builds below the April 2026 update", "ecosystem": "vendor"}, {"name": "microsoft windows 10 1607", "fixed": ["10.0.14393.9060"], "affected": "< 10.0.14393.9060", "ecosystem": "vendor"}, {"name": "microsoft windows 10 1809", "fixed": ["10.0.17763.8644"], "affected": "< 10.0.17763.8644", "ecosystem": "vendor"}, {"name": "microsoft windows 10 21h2", "fixed": ["10.0.19044.7184"], "affected": "< 10.0.19044.7184", "ecosystem": "vendor"}, {"name": "microsoft windows 10 22h2", "fixed": ["10.0.19045.7184"], "affected": "< 10.0.19045.7184", "ecosystem": "vendor"}, {"name": "microsoft windows 11 23h2", "fixed": ["10.0.22631.6936"], "affected": "< 10.0.22631.6936", "ecosystem": "vendor"}, {"name": "microsoft windows 11 24h2", "fixed": ["10.0.26100.8246"], "affected": "< 10.0.26100.8246", "ecosystem": "vendor"}, {"name": "microsoft windows 11 25h2", "fixed": ["10.0.26200.8246"], "affected": "< 10.0.26200.8246", "ecosystem": "vendor"}, {"name": "microsoft windows 11 26h1", "fixed": ["10.0.28000.1836"], "affected": "< 10.0.28000.1836", "ecosystem": "vendor"}, {"name": "microsoft windows server 2016", "fixed": ["10.0.14393.9060"], "affected": "< 10.0.14393.9060", "ecosystem": "vendor"}, {"name": "microsoft windows server 2019", "fixed": ["10.0.17763.8644"], "affected": "< 10.0.17763.8644", "ecosystem": "vendor"}, {"name": "microsoft windows server 2022", "fixed": ["10.0.20348.5020"], "affected": "< 10.0.20348.5020", "ecosystem": "vendor"}, {"name": "microsoft windows server 2022 23h2", "fixed": ["10.0.25398.2274"], "affected": "< 10.0.25398.2274", "ecosystem": "vendor"}, {"name": "microsoft windows server 2025", "fixed": ["10.0.26100.32690"], "affected": "< 10.0.26100.32690", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "ikev2", "infrastructure", "ipsec", "microsoft", "vpn", "windows"]
not_affected_if: ["ikev2-disabled", "no-ike-exposure", "udp-500-4500-blocked"]
published_at: "2026-04-14T18:17:34+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T23:44:52+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-33824", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-10-23T21:31:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33824", "first_seen_at": "2026-10-23T23:44:52+00:00"}]
---

# Double free in Windows IKE Extension allows an unauthorized attacker to execute code over a network

Double free (CWE-415) in the Windows IKEv2 service (IKEEXT), triggered by crafted IKEv2 fragment (SKF) packets sent to UDP 500/4500. Unauthenticated, no user interaction, CVSS 9.8. Patched in April 2026 Patch Tuesday (Apr 14). CISA added it to KEV on Aug 18, 2026. ZDI calls it wormable.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Microsoft Internet Key Exchange (IKE) Service Extensions affected ? fixed ?
- vendor:Windows IKE Service Extensions (IKEEXT) affected all supported Windows 10/11/Server builds below the April 2026 update fixed 10.0.14393.9060, 10.0.17763.8644, 10.0.19044.7184, 10.0.19045.7184, 10.0.22631.6936, 10.0.26100.8246, 10.0.26200.8246, 10.0.28000.1836
- vendor:microsoft windows 10 1607 affected < 10.0.14393.9060 fixed 10.0.14393.9060
- vendor:microsoft windows 10 1809 affected < 10.0.17763.8644 fixed 10.0.17763.8644
- vendor:microsoft windows 10 21h2 affected < 10.0.19044.7184 fixed 10.0.19044.7184
- vendor:microsoft windows 10 22h2 affected < 10.0.19045.7184 fixed 10.0.19045.7184
- vendor:microsoft windows 11 23h2 affected < 10.0.22631.6936 fixed 10.0.22631.6936
- vendor:microsoft windows 11 24h2 affected < 10.0.26100.8246 fixed 10.0.26100.8246
- vendor:microsoft windows 11 25h2 affected < 10.0.26200.8246 fixed 10.0.26200.8246
- vendor:microsoft windows 11 26h1 affected < 10.0.28000.1836 fixed 10.0.28000.1836
- vendor:microsoft windows server 2016 affected < 10.0.14393.9060 fixed 10.0.14393.9060
- vendor:microsoft windows server 2019 affected < 10.0.17763.8644 fixed 10.0.17763.8644
- vendor:microsoft windows server 2022 affected < 10.0.20348.5020 fixed 10.0.20348.5020
- vendor:microsoft windows server 2022 23h2 affected < 10.0.25398.2274 fixed 10.0.25398.2274
- vendor:microsoft windows server 2025 affected < 10.0.26100.32690 fixed 10.0.26100.32690

## How to check

Exposed if the host runs a build below the fixed build and has IKEv2 enabled and UDP 500/4500 reachable (VPN/RRAS server, IPsec policies). Check the build with 'winver' or '[System.Environment]::OSVersion.Version' against the fixed builds. Check the service with 'Get-Service IKEEXT'. Check listeners with 'Get-NetUDPEndpoint -LocalPort 500,4500'.

## Fix

Install the April 2026 or later cumulative update. Fixed builds: Win10 1607/Server 2016 10.0.14393.9060; Server 2019 10.0.17763.8644; Win10 21H2/22H2 10.0.19044.7184 and 10.0.19045.7184; Win11 23H2 10.0.22631.6936; Win11 24H2/Server 2025 10.0.26100.8246 (MSRC lists 10.0.26100.32690 for Server 2025); Win11 25H2 10.0.26200.8246; Win11 26H1 10.0.28000.1836. KBs per Rapid7: 24H2 KB5083769, 26H1 KB5083768, Win10 22H2/21H2 KB5082200, 1809 KB5082123, 1607 KB5082198, Server 2022 KB5082142. Workaround: block inbound UDP 500/4500 on systems that do not use IKE; otherwise allow it only from known peer addresses.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-33824
- 2026-10-23T21:31:44+00:00 analyst — Read the MSRC advisory (affected builds, mitigations), CVE.org, Rapid7 (KBs), ZDI and BleepingComputer. Network reachability of UDP 500/4500 is required, with IKEv2 enabled. MSRC page still shows Exploited: No (it is dated from first publication); KEV and BleepingComputer confirm exploitation. No public PoC found, but ZDI has a technical writeup. I did not search X or Bluesky. The KB list is from Rapid7, not read on MSRC; the Server 2025 build differs between MSRC and CVE.org, so verify it.
- 2026-10-23T23:44:52+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-33824

## Documents

- [advisory] MSRC CVE-2026-33824 https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33824
- [describes] ZDI: RCE in Windows IKEv2 https://www.thezdi.com/blog/2026/4/22/cve-2026-33824-remote-code-execution-in-windows-ikev2
- [discussion] BleepingComputer: IKE flaw now exploited https://www.bleepingcomputer.com/news/security/cisa-critical-windows-ike-extension-flaw-now-exploited-in-attacks/
- [mentions] CISA KEV addition 2026-08-18 https://www.cisa.gov/news-events/alerts/2026/08/18/cisa-adds-four-known-exploited-vulnerabilities-catalog

## From the sources

Microsoft Internet Key Exchange (IKE) Service Extensions contains a double free vulnerability that could enable remote code execution.

CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_