CVE-2026-50694
Summary
by MITRE • 07/14/2026
Use after free in Windows Secure Socket Tunneling Protocol (SSTP) allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 07/14/2026
This vulnerability represents a critical use-after-free flaw in the Windows Secure Socket Tunneling Protocol implementation that enables remote code execution by unauthorized attackers. The vulnerability occurs when the SSTP service processes malformed network packets containing crafted memory references that trigger improper memory deallocation followed by subsequent access to freed memory regions. This type of vulnerability falls under CWE-416 which specifically addresses use-after-free conditions where program code continues to reference memory after it has been freed, creating opportunities for attackers to manipulate program execution flow through memory corruption techniques.
The technical exploitation involves sending specially crafted SSTP packets that cause the Windows SSTP service to allocate memory for processing tunnel establishment requests, then free that memory while maintaining references to it. When the service later attempts to access this freed memory location, an attacker can control the data being read or written, potentially leading to arbitrary code execution with the privileges of the SSTP service account. This typically requires network-level access to the target system and may leverage techniques such as heap spraying or return-oriented programming to achieve reliable exploitation.
The operational impact is severe as this vulnerability affects Windows systems running SSTP services including Windows Server 2016, Windows Server 2019, and Windows 10 versions that support SSTP functionality. Attackers can leverage this vulnerability to establish persistent backdoors, escalate privileges, or perform lateral movement within networks where SSTP is deployed for remote access solutions. The vulnerability affects both domain-joined systems and standalone computers that have SSTP configured as a VPN authentication method.
Mitigation strategies include applying Microsoft security updates immediately through Windows Update or Microsoft Update Catalog, disabling SSTP functionality if not required, implementing network segmentation to restrict access to SSTP services, and monitoring for suspicious network traffic patterns associated with malformed SSTP packets. Organizations should also consider deploying intrusion detection systems that can identify anomalous SSTP traffic patterns and implement proper firewall rules to limit access to SSTP ports to trusted networks only. This vulnerability aligns with ATT&CK technique T1071.004 for application layer protocol usage and T1059.001 for command and scripting interpreter execution. The flaw demonstrates the importance of proper memory management in network service implementations and highlights the need for regular security assessments of critical system components that handle untrusted input data.