CVE-2026-70113 in Windows
Summary
by MITRE • 10/14/2026
Integer overflow or wraparound in Windows Client for NFS allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified involves a critical integer overflow condition within the Microsoft Windows Client for Network File System, commonly referred to as NFS client. This component is responsible for facilitating communication between Windows-based systems and remote servers utilizing the NFS protocol, which is predominantly found in Unix-like environments. The flaw stems from improper handling of numerical values during memory allocation or buffer management operations. Specifically, when processing certain inputs related to file attributes or directory structures received from an NFS server, the application fails to validate that the resulting integer value remains within acceptable bounds for a 32-bit signed integer. This oversight allows negative numbers or excessively large positive integers to be interpreted incorrectly by the underlying system logic, leading to miscalculations in buffer sizes or array indices.
From a technical perspective, this integer overflow represents a classic CWE-190 vulnerability type, where an arithmetic operation produces a result that exceeds the maximum value for the data type. In the context of Windows kernel-mode drivers and system services like the NFS client, such errors often translate into heap-based buffer overflows or stack corruption when the miscalculated size is used to allocate memory or copy data. An attacker who has already gained local access on the affected machine can craft a maliciously formatted response from an NFS server that triggers this overflow condition. By carefully controlling the input values, the adversary can manipulate the execution flow of the vulnerable process, potentially overwriting adjacent memory structures such as function pointers or exception handling routines.
The operational impact of exploiting this vulnerability is severe, primarily because it enables local privilege escalation to SYSTEM level access. Since the NFS client operates with high privileges within the Windows operating system environment, successfully leveraging this flaw allows an attacker to execute arbitrary code in a privileged context. This effectively bypasses standard user-level security controls and isolation mechanisms. Once elevated privileges are obtained, the attacker can install programs, view, change, or delete any data on the system, create new accounts with full administrative rights, and modify kernel memory structures. This level of access compromises the integrity, confidentiality, and availability of the entire host machine, turning a compromised user account into a complete takeover of the operating system.
In terms of threat modeling and adversary behavior, this vulnerability aligns closely with MITRE ATT&CK techniques related to privilege escalation via local exploits or abuse of elevated privileges. Attackers typically rely on such vulnerabilities after gaining initial foothold through phishing, network exploitation, or physical access. The ability to escalate from a standard user account to SYSTEM status significantly lowers the barrier for subsequent lateral movement and persistence mechanisms within an enterprise environment. Defenders must recognize that even services intended for interoperability with external systems can serve as vectors for internal compromise if they contain unchecked input validation logic.
Mitigation strategies should focus on immediate patching of the affected Windows components, ensuring that all security updates provided by Microsoft are applied promptly to address this specific integer overflow issue. Administrators should also consider disabling the NFS client feature entirely if it is not required for business operations, thereby reducing the attack surface. Network segmentation policies can further limit exposure by restricting access to NFS servers from untrusted or non-critical network segments. Additionally, implementing strict input validation and monitoring tools that detect anomalous behavior in system processes may help identify exploitation attempts before they result in full privilege escalation. Regular audits of installed features and adherence to the principle of least privilege for all user accounts remain essential practices to minimize the risk associated with such vulnerabilities.