CVE-2026-69794 in Windows
Summary
by MITRE • 09/09/2026
Buffer over-read in Windows Encrypting File System (EFS) allows an authorized attacker to disclose information locally.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified involves a buffer over-read condition within the Microsoft Windows Encrypting File System, commonly referred to as EFS. This component is responsible for providing file system-level encryption that protects data from unauthorized access by encrypting files on NTFS volumes before they are written to disk and decrypting them transparently when accessed by authorized users. The specific flaw arises during the processing of encrypted metadata or key containers, where the application fails to properly validate buffer boundaries before reading memory contents. This lack of rigorous bounds checking allows an attacker who has already gained local access with valid credentials to trigger a read operation that extends beyond the allocated memory space for the intended data structure.
From a technical perspective, this is classified as CWE-126, which denotes Buffer Over-read. Unlike buffer overflows that can lead to arbitrary code execution and privilege escalation through stack or heap corruption, an over-read primarily results in information disclosure. The attacker exploits the misalignment between expected and actual memory allocation sizes to extract sensitive data stored adjacent to the target buffer. In the context of EFS, this could potentially include partial contents of encryption keys, certificate details, or other cryptographic material that is not immediately accessible through standard API calls but resides in nearby memory regions allocated for related security operations.
The operational impact of this vulnerability centers on confidentiality rather than integrity or availability. An authorized attacker can leverage this flaw to disclose sensitive information locally without requiring elevated privileges beyond their current user context. While the attacker must already be authenticated, the ability to extract cryptographic secrets significantly undermines the core promise of EFS encryption. If an adversary obtains partial key material or related metadata, they may facilitate further attacks such as offline decryption attempts if other protective measures are weak, or use the disclosed information for lateral movement within a network environment where similar systems are deployed. This aligns with ATT&CK technique T1005, which covers Data from Local System, specifically under sub-techniques related to file and directory discovery or application data harvesting.
Mitigation strategies primarily involve applying vendor-supplied security patches that address the memory management logic within the EFS subsystem. Organizations should ensure that all systems are updated with the latest cumulative updates provided by Microsoft for their respective Windows versions. Additionally, since this vulnerability requires local access, enforcing strict physical and logical access controls is critical. Implementing multi-factor authentication for user accounts, restricting administrative privileges to only those who absolutely require them, and monitoring for unusual memory access patterns can help reduce the risk of exploitation. Regular security audits focusing on privilege escalation vectors and data exfiltration attempts are also recommended to detect any potential abuse of this flaw before it leads to significant data breaches.