CVE-2026-49793 in Windows
Summary
by MITRE • 07/14/2026
Heap-based buffer overflow 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
This heap-based buffer overflow vulnerability exists within the Windows Resilient File System implementation, representing a critical security flaw that can be exploited by authorized users with local access privileges. The vulnerability stems from improper input validation and memory management practices within the ReFS file system component, specifically when handling certain data structures during file operations or metadata processing. The flaw manifests as an insufficient bounds checking mechanism that allows attackers to write beyond allocated heap memory regions, potentially leading to arbitrary code execution within the privileged context of the operating system.
The technical exploitation of this vulnerability involves crafting malicious input or file structures that trigger the buffer overflow condition when processed by ReFS subsystem. Attackers can leverage this weakness to overwrite adjacent memory locations including function pointers, return addresses, or other critical control data structures within the heap memory layout. This type of vulnerability falls under CWE-121 Heap-based Buffer Overflow, which is classified as a common weakness in software security implementations where insufficient bounds checking allows memory corruption. The attack vector requires local system access and can be executed through legitimate user accounts since the vulnerability exists within authorized file system operations.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a means to execute arbitrary code with elevated privileges typically associated with system-level processes. Successful exploitation could lead to complete system compromise, persistent backdoor installation, or data exfiltration from systems running affected ReFS implementations. The vulnerability affects Windows operating systems that utilize ReFS as their primary file system, particularly those configured for high availability and fault tolerance scenarios where ReFS is commonly deployed. Organizations using ReFS for storage solutions or backup systems face heightened risk since these environments often contain sensitive data and critical operational information.
Mitigation strategies should focus on immediate patch deployment from Microsoft Security Updates, which address the specific heap overflow conditions in ReFS implementation. System administrators should implement the principle of least privilege and monitor for anomalous file system behavior that might indicate exploitation attempts. Network segmentation and endpoint detection measures can help identify potential exploitation activities within the local network environment. The vulnerability aligns with ATT&CK technique T1059 Command and Scripting Interpreter, where attackers may leverage local execution capabilities to establish persistent access. Additionally, this flaw demonstrates weakness in defensive programming practices that should include comprehensive input validation, memory safety checks, and regular security assessments of file system components to prevent similar vulnerabilities from being exploited in production environments.