CVE-2026-70207 in Windows
Summary
by MITRE • 10/14/2026
Heap-based buffer overflow in Network Policy Server (NPS) allows an authorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/16/2026
The vulnerability identified as a heap-based buffer overflow within the Microsoft Network Policy Server presents a critical security risk that compromises the integrity and availability of authentication infrastructure services. This specific flaw resides in how NPS processes certain requests, particularly those involving malformed or excessively large data structures intended for policy evaluation. When an authorized attacker interacts with this service over the network, they can supply crafted input that exceeds the allocated memory boundaries on the heap. The server fails to perform adequate bounds checking before copying this data into a fixed-size buffer, leading to adjacent memory being overwritten. This corruption of heap metadata or function pointers is the fundamental technical mechanism that allows for arbitrary code execution under the context of the service account running Network Policy Server.
From an operational perspective, the impact of exploiting this vulnerability extends far beyond simple denial of service. Because the attack vector requires network access and authorized credentials to initiate the interaction, it targets a high-value component responsible for validating user identities in enterprise environments utilizing RADIUS authentication. Successful exploitation grants the attacker the ability to execute arbitrary code on the vulnerable system with the privileges of the Network Policy Server process. This typically results in full control over the affected server, which can then be used as a pivot point to attack other systems within the internal network. The attacker could potentially harvest credentials stored or processed by NPS, modify authentication policies to bypass security controls, or establish persistent backdoors that remain undetected for extended periods due to the low-level nature of heap exploitation techniques.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-122, which describes a heap-based buffer overflow where data is written beyond the bounds of a heap-allocated memory region. The attack methodology corresponds to MITRE ATT&CK technique T1059, specifically command and script interpreters or system services abuse, as well as potential lateral movement via remote service exploitation such as T1210 if used for further network propagation. The requirement for authorization means this is not an unauthenticated remote code execution flaw but rather a privilege escalation vector from authenticated user to SYSTEM level access through memory corruption.
Mitigation strategies must focus on both immediate patching and long-term architectural hardening. Organizations should immediately apply the latest security updates provided by Microsoft that address this specific heap overflow in Network Policy Server. It is critical to ensure that all RADIUS clients are configured with strict input validation policies where possible, although server-side patches remain the primary defense. Additionally, network segmentation should be enforced to restrict access to NPS servers only from known and trusted authentication sources such as domain controllers or wireless LAN controllers. Implementing robust logging and monitoring for anomalous packet sizes directed at RADIUS ports can aid in early detection of exploitation attempts. Regular audits of service account permissions are also recommended to minimize the impact if a compromise occurs, ensuring that even with code execution, the attacker's ability to move laterally is constrained by least-privilege principles.