ZDI-26-622: Microsoft Windows IKEv2 AES-GCM Decryption Integer Underflow Remote Code Execution Vulnerability
Vulnerability: Unpatched Windows systems with IPsec are vulnerable to RCE via IKEv2 AES-GCM decryption integer underflow (CVE-2026-50696).
Deep Analysis and Expert Commentary
The vulnerability stems from improper input validation in the IKEEXT service, where malformed IKEv2 packets trigger an integer underflow during AES-GCM decryption. This memory corruption flaw enables arbitrary code execution in kernel context. Attackers can exploit this without authentication by sending crafted packets to vulnerable IPsec endpoints. While not all Windows systems use the affected IPsec configurations, exposed VPN gateways or site-to-site tunnels are prime targets. Beyond patching, network defenders should audit IPsec policies, restrict IKEv2 exposure to trusted networks, and monitor for anomalous packet patterns. The SYSTEM-level compromise potential makes this a critical infrastructure threat.
Action Items
- Apply Microsoft's security update for CVE-2026-50696 immediately
- Audit and harden IPsec/IKEv2 configurations in perimeter devices
- Implement network segmentation to limit IKEv2 exposure
Original Article Brief Intro
ZDI (Zero Day Initiative) · 2026-09-08 · Vulnerability: Unpatched Windows systems with IPsec are vulnerable to RCE via IKEv2 AES-GCM decryption integer underflow (CVE-2026-50696).
Related Terms and Notes
CVE IDs
- CVE-2026-50696
Techniques / TTPs
- RCE
- Zero-Day
Context Notes
- AES-GCM — Authenticated encryption algorithm used in IPsec implementations
- IKEEXT — Windows service managing IKE and AuthIP for IPsec key exchange
- IKEv2
- IPsec
- IPsec Vulnerability
- Remote Code Execution
- Windows
- Windows Security