CVE-2026-49789 in Windows
Summary
by MITRE • 07/14/2026
Stack-based buffer overflow in Windows NTFS allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 07/14/2026
This vulnerability represents a critical stack-based buffer overflow condition within the Windows NTFS file system implementation that enables local privilege escalation for authenticated attackers. The flaw occurs when the operating system processes certain file system operations that involve stack memory allocation, where input validation fails to properly restrict the amount of data copied into fixed-size stack buffers. This specific weakness allows an attacker with legitimate user credentials to exploit the vulnerability and gain elevated privileges on the target system.
The technical implementation of this vulnerability stems from improper bounds checking during NTFS file system processing operations. When legitimate users perform file operations such as directory traversal, file renaming, or metadata manipulation, the system fails to validate the length of user-supplied data before copying it into stack-based memory structures. This creates an exploitable condition where crafted input can overwrite adjacent stack memory including return addresses and control information, enabling attackers to redirect program execution flow. The vulnerability is classified under CWE-121 Stack-based Buffer Overflow, which specifically addresses buffer overflows occurring in stack memory regions.
The operational impact of this vulnerability extends beyond simple local privilege escalation as it provides attackers with a reliable method to bypass standard security controls within the Windows operating system. Once successfully exploited, the attacker gains elevated privileges that typically include administrative rights, allowing them to access sensitive system resources, modify critical files, install malicious software, and potentially establish persistent backdoors. The local nature of this attack means that only users who already have legitimate access to the system need to be compromised, making it particularly dangerous in environments where user accounts are shared or where initial access can be obtained through social engineering or other means.
From a defensive standpoint, mitigations for this vulnerability should include immediate application of Microsoft security patches and updates specifically addressing the NTFS buffer overflow condition. System administrators should implement least privilege principles to limit the potential impact of successful exploitation, ensuring that user accounts have minimal necessary permissions. Additionally, enabling stack protection mechanisms such as stack canaries and address space layout randomization can significantly reduce exploit reliability. Organizations should also monitor for anomalous file system activity patterns that might indicate exploitation attempts and maintain comprehensive logging of privileged operations for forensic analysis purposes. The vulnerability aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel or system-level vulnerabilities, making it a high-priority target for security teams to address through both reactive patching and proactive monitoring strategies.