Unauthenticated Double-Free RCE in Microsoft Windows IKE Extension
CISA: Microsoft Internet Key Exchange (IKE) Service Extensions Double Free Vulnerability
CVSS 3.1
9.8critical
EPSS
73%p99
Published
()
KEV added
AI analysis
A double-free memory-corruption flaw (CWE-415) in the Microsoft Windows Internet Key Exchange (IKE) service extension allows a remote, unauthenticated attacker to trigger the bug with crafted network traffic, with no privileges or user interaction required. Successful exploitation yields remote code execution with full system impact, reflected in the critical 9.8 CVSS score (high confidentiality, integrity, and availability). The vulnerable IKE component is present in Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (23H2, 24H2, 25H2, 26H1), and Windows Server 2016, 2019, and 2022 (including 23H2), which ship it as a built-in feature. CISA added the flaw to the Known Exploited Vulnerabilities catalog on 2026-08-18, and security reporting confirms it is being actively exploited in the wild, though ransomware use is not yet confirmed. No public proof-of-concept is known, but the high EPSS score (72.7%, 99th percentile) signals a very strong likelihood of imminent or ongoing exploitation.
What to do: Apply Microsoft's security updates for CVE-2026-33824 to all affected Windows 10, Windows 11, and Windows Server releases, prioritizing internet-exposed systems where IKE/VPN is reachable (UDP 500/4500), per BOD 26-04 requirements. Organizations unable to patch promptly should restrict or discontinue use of exposed IKE/VPN services on affected hosts until updated. Triage VPN endpoints and remote-access servers for crashes or suspicious IKE traffic given confirmed in-the-wild exploitation.
Affected
Microsoft Windows 10
1607
Microsoft Windows 10
1809
Microsoft Windows 10
21H2
Microsoft Windows 10
22H2
Microsoft Windows 11
23H2
Microsoft Windows 11
24H2
Microsoft Windows 11
25H2
Microsoft Windows 11
26H1
Microsoft Windows Server
2016
Microsoft Windows Server
2019
Microsoft Windows Server
2022
Microsoft Windows Server
2022 (23H2)
Estimated exposure
masswell over 1B Windows devices include the built-in IKE extension; internet-exposed VPN/IKE endpoints plausibly number in the hundreds of thousands — IKE is a built-in Windows component present in every listed Windows 10/11/Server release, whose combined install base exceeds a billion devices, and the subset reachable over the network (VPN gateways and remote-access hosts) remains far…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
Double free in Windows IKE Extension allows an unauthorized attacker to execute code over a network.
CISA Known Exploited Vulnerability
Affected
Microsoft Internet Key Exchange (IKE) Service Extensions
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.
windows 10 1607, windows 10 1809, windows 10 21h2, windows 10 22h2, windows 11 23h2, windows 11 24h2, windows 11 25h2, windows 11 26h1, windows server 2016, windows server 2019, windows server 2022, windows server 2022 23h2
CISA warns CVE-2026-33824, a critical unprivileged RCE in Windows IKE Extension, is now actively exploited.
CVE-2026-33824 is a critical remote code execution vulnerability in the Windows IKE Extension affecting all supported Windows 10, Windows 11, and Windows Server releases. The flaw allows unprivileged attackers to gain code execution on affected systems. CISA has flagged the vulnerability as actively exploited in attacks, indicating a KEV addition and urgent patching priority for Windows environments.
CISA added four critical actively exploited flaws to KEV: macOS Screen Sharing, SharePoint, VMware vCenter, and Microsoft IKE, with APT and ransomware use.
CISA added CVE-2026-65400 (macOS Screen Sharing, CVSS 9.8), CVE-2026-55040 (SharePoint, CVSS 9.1), CVE-2026-59310 (VMware vCenter, CVSS 9.8) and CVE-2026-33824 (Microsoft IKE Service Extensions, CVSS 9.8) to the KEV catalog. The macOS flaw was abused to deliver a Monero miner, while the vCenter bug was exploited by a suspected China-nexus APT to install reverse_ssh backdoors and Babuk-derived ransomware across 361 victim IPs in 47 countries. Unit 42 linked CVE-2026-33824 to a Chinese-speaking actor running an AI-enabled campaign using DeepSeek. FCEB agencies must patch by August 21, 2026 under BOD 26-04.
CISA adds actively exploited flaws in Microsoft IKE, SharePoint, VMware vCenter, and macOS Screen Sharing to KEV catalog, due August 21.
CISA added four vulnerabilities to its Known Exploited Vulnerabilities catalog: CVE-2026-33824 (Windows IKE remote code execution, CVSS 9.8), CVE-2026-55040 (SharePoint JWT authentication bypass, CVSS 9.1), CVE-2026-59310 (VMware vCenter Syslog path traversal, CVSS 9.8), and CVE-2026-65400 (macOS Screen Sharing improper authentication). The SharePoint flaw combines four weaknesses including alg:none JWT forging to impersonate any user, with Defused researchers observing attackers using Rapid7's PoC against honeypots. The Dutch NCSC confirmed active exploitation of the macOS Screen Sharing flaw on August 15, 2026. Federal agencies must patch by August 21, 2026.
CISA added four actively exploited vulnerabilities to its KEV catalog, headlined by CVE-2026-33824, a Windows IKE Service Extensions remote code execution flaw.
CISA's KEV addition, dated August 18, covers CVE-2026-33824 in Windows IKE Service Extensions, CVE-2026-55040 in on-premises Microsoft SharePoint Server, CVE-2026-59310 in Broadcom VMware vCenter, and CVE-2026-65400 in Apple macOS Screen Sharing. KEV listing confirms observed exploitation in the wild. Three of the four products are frequently deployed as high-value enterprise infrastructure, including remote-access endpoints and collaboration platforms.
ZDI details CVE-2026-33824, a double-free in Windows IKEv2 fragment reassembly enabling unauthenticated remote code execution as SYSTEM on Windows.
Zero Day Initiative published technical analysis of CVE-2026-33824, a double-free in the Windows IKE Extension (ikeext.dll) caused by improper ownership handling of a heap blob pointer during IKEv2 fragment reassembly in IkeReinjectReassembledPacket(). A remote unauthenticated attacker can send a crafted IKE_SA_INIT message with a Security Realm Vendor ID followed by fragmented IKE_AUTH payloads to trigger the double free. Successful exploitation could yield arbitrary code execution under the IKEEXT service context (SYSTEM). ZDI also provided IDS detection guidance correlating the two-packet sequence on UDP ports 500 and 4500.