CVE-2026-73024 in Windows
Summary
by MITRE • 09/09/2026
Heap-based buffer overflow in Windows Services for NFS ONCRPC XDR Driver allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified involves a heap-based buffer overflow within the ONC/RPC XDR driver component of Microsoft's Services for Network File System, commonly referred to as NFS on Windows systems. This specific flaw resides in how the driver processes external input data during the decoding and encoding operations inherent to the External Data Representation protocol used by ONC/RPC services. When an attacker interacts with this service, they can supply crafted network packets or local system calls that contain malformed XDR-encoded data structures exceeding the allocated buffer size on the heap. This discrepancy causes the driver to write data beyond the boundaries of the intended memory allocation, corrupting adjacent heap metadata and potentially overwriting critical control structures such as function pointers or exception handlers stored in nearby memory regions.
From a technical perspective, this is classified under CWE-122, which denotes a heap-based buffer overflow allowing for arbitrary code execution conditions when combined with specific exploitation techniques like heap spraying or targeted overwrite attacks. The vulnerability stems from insufficient bounds checking during the parsing of RPC request parameters. Because the Services for NFS feature enables Windows systems to act as both clients and servers in an NFS environment, it exposes attack surfaces that are not present on default installations where this role is disabled. An attacker who has already gained local access can leverage this flaw to execute arbitrary code within the context of the Local System account or other privileged service accounts depending on how the NFS server component is configured and which privileges are assigned to the initiating process.
The operational impact of successfully exploiting this vulnerability is significant, primarily centered around privilege escalation from a standard user level to that of an administrator or system-level entity. Once local code execution is achieved through memory corruption techniques such as controlling the return address on the stack via heap metadata overwrite, the attacker gains full control over the affected Windows host. This allows for the installation of malware, creation of new administrative accounts, exfiltration of sensitive data stored locally, and potentially using the compromised machine as a pivot point to attack other systems within the internal network infrastructure. The ability to escalate privileges without requiring additional authentication vectors makes this a high-severity issue in environments where NFS services are actively deployed for file sharing across heterogeneous operating system landscapes.
Mitigation strategies focus on reducing the attack surface by disabling unnecessary features and applying timely security patches. Organizations should evaluate whether the Services for NFS feature is required; if not, it should be uninstalled via the Windows Features dialog or through PowerShell cmdlets to remove the vulnerable driver from memory entirely. For environments where NFS services are essential, administrators must ensure that all relevant cumulative updates provided by Microsoft addressing this specific heap overflow in the ONC/RPC XDR processing logic are installed promptly. Additionally, implementing strict network segmentation policies can limit exposure by restricting access to NFS ports only from trusted subnets and enforcing strong authentication mechanisms for any remote connections attempting to interact with these services. Regular vulnerability scanning focused on unpatched Windows components remains critical for detecting potential exploitation attempts before they result in full system compromise.