CVE-2026-50696: Windows 10 1809 IKE Protocol DOS Flaw

CVE-2026-50696 Overview

CVE-2026-50696 is a heap-based buffer overflow vulnerability in the Windows Internet Key Exchange (IKE) Protocol implementation. The flaw allows an unauthenticated remote attacker to trigger a denial-of-service condition by sending crafted IKE traffic to an affected system over the network. No user interaction or prior authentication is required to exploit this issue. Microsoft has classified the vulnerability under CWE-122: Heap-based Buffer Overflow. The vulnerability affects a broad range of currently supported Windows client and server operating systems, including Windows 10, Windows 11, Windows Server 2019, Windows Server 2022, and Windows Server 2025.

Critical Impact
An unauthenticated network attacker can crash the IKE service on affected Windows hosts, disrupting IPsec VPN connectivity and dependent services.

Affected Products

Microsoft Windows 10 (versions 1809, 21H2, 22H2)
Microsoft Windows 11 (versions 24H2, 25H2, 26H1)
Microsoft Windows Server 2019, 2022, and 2025

Discovery Timeline

2026-07-14 - CVE-2026-50696 published to NVD
2026-07-16 - Last updated in NVD database

Technical Details for CVE-2026-50696

Vulnerability Analysis

The vulnerability resides in the Windows implementation of the Internet Key Exchange (IKE) protocol, which negotiates security associations for IPsec tunnels. A heap-based buffer overflow occurs when the IKE service processes a malformed protocol message. The overflow corrupts heap memory used by the IKE service, leading to a service crash and denial of service. Because IKE runs as a privileged system component and listens for network traffic on UDP ports 500 and 4500, an attacker can reach the vulnerable code path without authentication. The advisory scope is limited to availability impact; confidentiality and integrity are not affected according to Microsoft's assessment.

Root Cause

The root cause is improper size validation on heap-allocated buffers when parsing incoming IKE payloads. When an oversized or malformed payload is copied into an undersized heap buffer, adjacent heap metadata or allocations are overwritten. The Windows heap manager detects the corruption or the service faults during subsequent access, terminating the IKE service process. This class of defect is tracked under CWE-122.

Attack Vector

Exploitation is performed remotely over the network. An attacker sends a crafted IKE packet to UDP port 500 or 4500 on a target running an affected Windows version with IPsec or IKE-based VPN services active. The attack requires no privileges and no user interaction. Successful exploitation halts IKE processing, breaking VPN connectivity and any dependent IPsec-protected communications until the service or host is restarted. Refer to the Microsoft Security Update CVE-2026-50696 advisory for authoritative technical details.

Detection Methods for CVE-2026-50696

Indicators of Compromise

Unexpected termination or repeated restarts of the IKE and AuthIP Keying Modules service (IKEEXT) recorded in the Windows Service Control Manager event log.
Application or system crash dumps referencing the ikeext.dll module with heap corruption exception codes such as 0xC0000374.
Sudden loss of active IPsec or VPN sessions coinciding with inbound UDP 500 or 4500 traffic from untrusted sources.

Detection Strategies

Monitor for anomalous inbound UDP 500 and 4500 traffic volumes or malformed ISAKMP headers using network sensors or IDS signatures.
Alert on Windows Event ID 7031 or 7034 for the IKEEXT service to detect unexpected service failures.
Correlate VPN gateway availability metrics with edge firewall logs to identify DoS attempts targeting IKE endpoints.

Monitoring Recommendations

Enable telemetry on Windows Server VPN endpoints to capture service crash events and forward them to a centralized SIEM.
Baseline normal IKE traffic patterns so that spikes or protocol anomalies trigger alerts.
Track patch compliance across all Windows 10, Windows 11, and Windows Server systems that expose IKE services to untrusted networks.

How to Mitigate CVE-2026-50696

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-50696 to all affected Windows client and server systems.
Prioritize patching internet-facing VPN gateways and any host exposing UDP 500 or 4500 to untrusted networks.
Inventory systems running the IKEEXT service and verify patch deployment status through configuration management tooling.

Patch Information

Microsoft has published fixes through the standard security update channels. Consult the Microsoft Security Update CVE-2026-50696 page for the specific KB article and build numbers that address the vulnerability on each affected Windows version. Install updates via Windows Update, WSUS, Microsoft Update Catalog, or your enterprise patch management platform.

Workarounds

Restrict inbound UDP 500 and 4500 traffic at perimeter firewalls to known VPN peers only, blocking arbitrary internet sources.
Disable the IKEEXT service on systems that do not require IPsec or IKE-based VPN functionality until patching is complete.
Place vulnerable IKE endpoints behind an intermediary VPN concentrator or filtering device capable of validating IKE payloads.

bash

# Example: restrict IKE traffic to trusted peers using Windows Firewall
New-NetFirewallRule -DisplayName "Allow IKE from VPN Peer" -Direction Inbound -Protocol UDP -LocalPort 500,4500 -RemoteAddress 203.0.113.10 -Action Allow
New-NetFirewallRule -DisplayName "Block IKE from Untrusted" -Direction Inbound -Protocol UDP -LocalPort 500,4500 -Action Block