CVE-2026-50407 in Windows
Summary
by MITRE • 07/14/2026
Heap-based buffer overflow in Windows Resilient File System (ReFS) allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 07/15/2026
A heap-based buffer overflow vulnerability exists within the Windows Resilient File System implementation that enables authenticated attackers to achieve local privilege escalation. This flaw resides in how ReFS handles certain memory operations during file system processing, specifically when managing heap allocations for metadata structures. The vulnerability stems from insufficient bounds checking in memory allocation routines that process file system transactions and directory entries. When an authenticated user executes crafted operations against ReFS volumes, the system fails to properly validate input parameters before copying data into heap-allocated buffers, resulting in memory corruption that can be exploited to execute arbitrary code with elevated privileges.
The technical implementation of this vulnerability follows a classic heap overflow pattern where attacker-controlled data exceeds the bounds of allocated heap memory regions. The flaw manifests during ReFS file system operations such as directory creation, file manipulation, or metadata updates where input validation is insufficient. The vulnerability maps to common weakness enumerations including CWE-121 Heap-based Buffer Overflow and CWE-787 Out-of-bounds Write, both of which are categorized under the broader category of buffer overflow conditions. Attackers can leverage this weakness by constructing malicious file system operations that trigger the vulnerable code path, potentially leading to arbitrary code execution in kernel mode with SYSTEM privileges.
From an operational perspective, this vulnerability represents a significant threat to Windows environments utilizing ReFS file systems, particularly in server and enterprise configurations where privileged accounts are common. The local privilege escalation vector means that attackers must first establish a foothold on the target system through legitimate authentication mechanisms such as user accounts or service accounts. Once exploited, the vulnerability allows attackers to gain SYSTEM-level access without requiring additional exploitation techniques or complex attack chains. This makes it particularly dangerous in environments where ReFS is used for critical data storage and where privileged accounts may have elevated access to sensitive systems.
The exploitability of this vulnerability aligns with ATT&CK technique T1068, which describes the use of privilege escalation through local exploits. Security professionals should recognize that successful exploitation can lead to complete system compromise, potentially enabling lateral movement within networks or access to sensitive data repositories. Mitigation strategies include applying Microsoft security patches promptly, implementing least privilege principles for file system operations, and monitoring for anomalous ReFS usage patterns in network logs. System administrators should also consider disabling ReFS on systems where the risk of exploitation outweighs its benefits, particularly in environments with less stringent security controls or where legacy applications may be vulnerable to similar heap-based attacks. Regular vulnerability assessments and penetration testing can help identify systems running vulnerable ReFS implementations before they become targets for exploitation.