CVE-2026-83585 in Windows
Summary
by MITRE • 10/14/2026
Use of externally-controlled format string in Windows NTFS allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described involves the improper handling of user-supplied input within the New Technology File System (NTFS) driver on Microsoft Windows operating systems, specifically classified as a use of externally controlled format string. This flaw arises when the NTFS component processes data from an authenticated source without adequately sanitizing or validating special characters that are interpreted as formatting directives by underlying C-style library functions such as printf or similar logging mechanisms. In this context, an authorized attacker who has already gained access to the system can exploit this weakness by crafting specific file names or metadata structures within a volume managed by NTFS. When these crafted inputs are processed during standard filesystem operations like directory listing, attribute retrieval, or log generation, they trigger unintended execution paths due to the misinterpretation of format specifiers embedded in the input data.
From a technical perspective, this vulnerability falls under CWE-134: Use of Externally-Controlled Format String, which is categorized as an Input Validation error where user-controlled input is passed directly into a function that interprets it as a format string rather than plain text. The operational impact of exploiting this flaw can be severe, potentially leading to local privilege escalation if the attacker can manipulate memory contents or control flow through stack-based buffer overflows often associated with such format string abuses. By carefully constructing payloads containing specific sequence characters like %x or %n, an attacker may read arbitrary kernel memory locations or write data to arbitrary addresses, thereby bypassing standard security controls and gaining higher-level permissions than originally granted. This aligns with the MITRE ATT&CK technique T1068: Exploitation for Privilege Escalation, where adversaries leverage software vulnerabilities to increase their access level on a compromised host.
The presence of this vulnerability highlights critical gaps in input validation practices within core operating system components that handle high-volume or complex data structures like filesystem metadata. Although the initial attack vector requires authentication, meaning it is not remotely exploitable without prior compromise, the ability to escalate privileges from a standard user account to SYSTEM level represents a significant security risk for multi-user environments and servers where least-privilege principles are enforced. Attackers can leverage this elevation to install persistent backdoors, dump credential hashes using tools like Mimikatz, or disable security monitoring agents, effectively taking full control of the affected system.
Mitigation strategies primarily involve applying vendor-supplied patches that address the root cause by implementing strict input validation and sanitization routines within the NTFS driver codebase. Administrators should ensure that all Windows systems are updated with the latest cumulative updates provided by Microsoft to close this specific gap in format string handling. Additionally, enforcing least-privilege policies can limit the blast radius of such an exploit; if users operate under restricted accounts without administrative rights or elevated privileges, the potential for successful privilege escalation is significantly reduced even if the vulnerability exists. Regular auditing of system logs and monitoring for anomalous filesystem activities can also aid in detecting attempts to exploit this flaw before significant damage occurs.