CVE-2026-54109 in Windows
Summary
by MITRE • 07/14/2026
Integer overflow or wraparound in Windows Resilient File System (ReFS) allows an authorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 07/14/2026
The vulnerability described represents a critical integer overflow condition within the Windows Resilient File System implementation that enables local privilege escalation through code execution. This flaw exists in the way ReFS handles numerical calculations during file system operations, specifically when processing certain data structures that require integer arithmetic. The vulnerability manifests when an attacker with legitimate access to the system can manipulate file system operations to cause integer wraparound conditions that subsequently lead to memory corruption and arbitrary code execution.
The technical root cause of this issue stems from insufficient input validation and overflow checking within ReFS kernel components. When processing specific file attributes or metadata structures, the system performs arithmetic operations on integer values that do not properly account for potential overflow conditions. This aligns with common weakness patterns identified in CWE-190, which addresses integer overflow and wraparound vulnerabilities. The flaw operates at the kernel level within the ReFS file system driver, making it particularly dangerous as it can be exploited by any authenticated user who can interact with the file system.
From an operational perspective, this vulnerability creates a significant attack surface for malicious actors who already possess legitimate credentials to the system. The local execution requirement means that attackers cannot exploit this remotely but must have some form of system access or presence on the target machine. However, once exploited, the privilege escalation potential allows attackers to gain elevated system privileges and potentially establish persistent access. This vulnerability directly maps to ATT&CK technique T1068 which covers local privilege escalation through kernel exploits, and T1547 which involves establishing persistence through system-level components.
The exploitation process typically involves crafting specific file operations or metadata structures that trigger the integer overflow condition during ReFS processing. Attackers may manipulate file sizes, directory structures, or other numerical parameters within the file system to force the wraparound behavior. The resulting memory corruption can then be leveraged to overwrite critical function pointers or execute shellcode in kernel space. This type of vulnerability is particularly concerning because it operates below the level of typical user-space protections and can bypass many standard security mechanisms including address space layout randomization and data execution protection.
Mitigation strategies for this vulnerability require a multi-layered approach focusing on both immediate patching and operational security improvements. Microsoft has released security updates addressing this specific integer overflow issue, and system administrators should prioritize applying these patches to all affected Windows systems running ReFS. Additionally, implementing least privilege principles can limit the potential impact of exploitation by reducing the number of users with legitimate access to ReFS-enabled volumes. Network segmentation and monitoring for unusual file system activity patterns can help detect potential exploitation attempts. The vulnerability also underscores the importance of kernel-mode code review processes and formal verification techniques that can identify similar integer overflow conditions in other system components, particularly those handling numerical calculations in security-critical paths.