CVE-2026-62889 in Windows
Summary
by MITRE • 08/11/2026
Double 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 • 08/11/2026
This vulnerability represents a critical double free error within the Windows Secure Socket Tunneling Protocol implementation that enables remote code execution by unauthenticated attackers. The flaw occurs when the SSTP service processes incoming network packets containing malformed data structures, specifically in the memory management routines responsible for handling tunnel establishment and authentication sequences. When an attacker crafts malicious SSTP frames with duplicate memory deallocation requests, the system's heap management becomes corrupted, creating opportunities for arbitrary code execution.
The technical nature of this vulnerability aligns with CWE-415, which describes improper behavior during memory deallocation operations where a program attempts to free the same memory block twice. This condition leads to heap corruption that can be exploited by attackers to manipulate program flow and execute malicious payloads. The SSTP protocol operates at layer 3 of the network stack, making it particularly dangerous as it can be triggered through standard network traffic without requiring authentication or prior access to the target system.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables full system compromise from remote locations. Attackers can leverage this weakness to deploy malware, establish persistent backdoors, or conduct lateral movement within networks where Windows SSTP services are enabled. The vulnerability affects systems running Windows Server 2012 and later versions, particularly those configured with SSTP-based VPN servers that handle untrusted network traffic from external sources.
According to ATT&CK framework category T1210, this vulnerability maps directly to exploitation of remote services and can be classified under technique T1059 for command and control communication. The attack chain typically involves initial reconnaissance to identify vulnerable systems, followed by crafting malicious SSTP packets that trigger the double free condition during normal protocol operation. Network defenders must understand that this vulnerability operates at the transport layer without requiring authentication, making traditional perimeter defenses insufficient.
Mitigation strategies should include immediate deployment of Microsoft security patches addressing the specific heap corruption issues in the SSTP implementation. Organizations should disable SSTP services on systems where they are not required and implement network segmentation to limit exposure. The use of intrusion detection systems capable of identifying malformed SSTP traffic patterns can provide early warning of exploitation attempts. Additionally, monitoring for unusual memory allocation patterns and implementing heap protection mechanisms such as guard pages can reduce the effectiveness of exploitation attempts.
The vulnerability demonstrates how legacy protocol implementations can contain critical security flaws that persist across multiple versions of operating systems. Organizations must maintain comprehensive patch management programs specifically targeting VPN and tunneling protocols, as these services often remain enabled by default on enterprise systems. Regular security assessments should include testing for similar memory corruption vulnerabilities in other network services, particularly those implementing complex stateful protocols that handle external network input.
This particular vulnerability highlights the importance of rigorous code review processes for protocol implementations, especially in kernel-level components where memory management errors can have severe consequences. The double free condition represents a classic example of how seemingly minor programming errors in resource management can create significant security risks, emphasizing the need for thorough testing methodologies including fuzzing and formal verification techniques to identify such conditions before deployment.