CVE-2026-59128 in Windows
Summary
by MITRE • 08/11/2026
Out-of-bounds read in Windows Encrypting File System (EFS) allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 08/12/2026
The vulnerability under discussion represents a critical out-of-bounds read flaw within the Windows Encrypting File System EFS component that enables authenticated attackers to potentially access sensitive information on compromised systems. This issue specifically affects the EFS implementation in Microsoft Windows operating systems and demonstrates how improper bounds checking in cryptographic file handling can create security risks for legitimate users. The vulnerability exists within the file encryption and decryption processes where the system fails to properly validate array indices or buffer boundaries during EFS operations, leading to memory access violations that could be exploited for information disclosure purposes.
From a technical perspective, this out-of-bounds read occurs when the EFS subsystem attempts to process encrypted files or certificates without adequate validation of input parameters or buffer limits. The flaw manifests during normal EFS operations such as file encryption, decryption, or certificate processing where the system reads memory locations beyond the intended data boundaries. This type of vulnerability typically arises from insufficient bounds checking in memory management routines and can be classified under CWE-129 Input Validation and Bounds Checking. The attack vector requires local authentication since only authorized users with legitimate access to the system can trigger the vulnerable code path, making this a local privilege escalation or information disclosure threat rather than a remote exploit.
The operational impact of this vulnerability extends beyond simple information disclosure as it potentially allows attackers to extract sensitive data from memory locations that should remain protected. Attackers could leverage this weakness to recover encryption keys, certificate information, or other cryptographic material stored in memory during EFS operations. The implications are particularly concerning given that EFS is designed to provide transparent file encryption for Windows systems, meaning that any compromise of the underlying implementation undermines the security guarantees that users expect from the system. This vulnerability aligns with ATT&CK technique T1003 Credential Dumping and T1059 Command and Scripting Interpreter, as attackers may use such information to further compromise systems or escalate privileges.
Mitigation strategies for this vulnerability should focus on implementing proper bounds checking mechanisms within the EFS subsystem and ensuring that all memory access operations validate array indices against buffer limits. Microsoft has addressed this issue through security updates that correct the out-of-bounds read behavior in the encryption handling routines, requiring system administrators to apply these patches promptly. Additional protective measures include monitoring for unusual EFS activity patterns, implementing least privilege principles for file system access, and ensuring that only authorized users have access to systems where EFS is actively used. Organizations should also consider reviewing their encryption practices and ensuring that cryptographic material is properly protected even when operating within the bounds of legitimate system functionality. The vulnerability highlights the importance of proper input validation in cryptographic implementations and serves as a reminder that even trusted system components can contain security flaws that require careful attention to prevent exploitation by authenticated attackers.