CVE-2025-49721 in Windows
Summary
by MITRE • 07/08/2025
Heap-based buffer overflow in Windows Fast FAT Driver allows an unauthorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 08/23/2025
This vulnerability resides in the Windows Fast FAT driver component which handles file system operations for fat formatted volumes. The heap-based buffer overflow occurs when the driver processes malformed input data during file system operations, specifically when handling certain file names or directory structures that exceed allocated memory boundaries. The flaw represents a classic heap corruption vulnerability where insufficient bounds checking allows an attacker to overwrite adjacent memory locations in the driver's heap allocation. This type of vulnerability is categorized under CWE-121 heap-based buffer overflow which directly enables arbitrary code execution within the kernel context. The attack requires local system access since the vulnerability exists within a kernel-mode driver component that operates with elevated privileges. Once exploited, the attacker can execute code with SYSTEM level privileges, effectively bypassing standard user account controls and gaining complete control over the affected system. The operational impact extends beyond simple privilege escalation as this vulnerability could be leveraged to establish persistent backdoors, disable security features, or exfiltrate sensitive data from the compromised system.
The technical exploitation of this vulnerability follows established patterns documented in various threat intelligence reports and ATT&CK framework techniques for privilege escalation. Attackers typically craft malicious file names or directory structures that trigger the buffer overflow condition when processed by the fat driver. The heap corruption can be manipulated to overwrite critical function pointers or return addresses within the kernel memory space, enabling code execution with elevated privileges. This vulnerability is particularly concerning because it operates at the kernel level where standard operating system protections are bypassed. The Fast FAT driver's implementation likely lacks proper input validation mechanisms that would normally prevent such buffer overflows from occurring in user-mode applications. Security researchers have identified this class of vulnerability as a common vector for local privilege escalation attacks, with similar patterns observed in other Windows kernel drivers. The exploitation process typically involves precise memory layout knowledge and may require multiple attempts to achieve reliable code execution due to heap randomization techniques implemented by modern operating systems.
Mitigation strategies for this vulnerability should focus on both immediate patching and operational security improvements. Microsoft has released security updates that address the specific heap overflow condition in the Fast FAT driver, requiring system administrators to apply these patches promptly across all affected systems. Organizations should implement comprehensive vulnerability management processes that include regular scanning for unpatched systems and prioritization of kernel-level vulnerabilities. Network segmentation and least privilege principles can help limit the potential impact if exploitation occurs, though this is primarily a local privilege escalation vector. System monitoring solutions should be configured to detect anomalous file system activity patterns that might indicate exploitation attempts, particularly around FAT volume operations. The use of exploit prevention technologies such as control flow integrity checks and address space layout randomization can provide additional layers of defense against exploitation attempts. Security teams should also conduct regular penetration testing and vulnerability assessments focusing on kernel-mode components to identify similar vulnerabilities before they can be exploited by adversaries. Implementation of automated patch management systems ensures that critical security updates are deployed consistently across all endpoints without delay, reducing the window of opportunity for attackers to exploit known vulnerabilities.