CVE-2015-7359 in Truecrypt
Summary
by MITRE
The (1) IsVolumeAccessibleByCurrentUser and (2) MountDevice methods in Ntdriver.c in TrueCrypt 7.0, VeraCrypt before 1.15, and CipherShed, when running on Windows, do not check the impersonation level of impersonation tokens, which allows local users to impersonate a user at SecurityIdentify level and gain access to other users' mounted encrypted volumes.
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Analysis
by VulDB Data Team • 12/30/2022
The vulnerability described in CVE-2015-7359 represents a critical access control flaw in disk encryption software that affects TrueCrypt 7.0, VeraCrypt before 1.15, and CipherShed implementations on Windows systems. This issue stems from inadequate security token validation within the kernel-mode drivers responsible for volume access operations. The vulnerability specifically impacts two critical methods within the Ntdriver.c file where the IsVolumeAccessibleByCurrentUser and MountDevice functions fail to properly verify the impersonation level of security tokens used during volume access operations.
The technical flaw manifests when local users exploit the missing impersonation level checks to escalate their privileges and gain unauthorized access to encrypted volumes belonging to other user accounts. This occurs because the affected software components do not validate whether the current security token has sufficient privileges to access the target volume, allowing attackers to impersonate users at the SecurityIdentify level. The SecurityIdentify level represents a relatively low security context that typically permits basic identification but not full access rights, yet the flawed implementation permits this level to bypass normal access controls for encrypted volume mounting operations.
From an operational perspective, this vulnerability creates significant security risks for multi-user systems where different users maintain encrypted volumes containing sensitive data. An attacker with local access can exploit this weakness to access other users' encrypted volumes without proper authentication, effectively bypassing the core security mechanism that encryption software is designed to provide. This represents a privilege escalation vulnerability that can lead to data exposure, information disclosure, and potential compromise of sensitive information stored in encrypted volumes. The impact extends beyond simple data access, as it undermines the fundamental trust model that disk encryption systems rely upon to protect user data.
The vulnerability aligns with CWE-284, which addresses improper access control issues in software systems, and demonstrates characteristics consistent with ATT&CK technique T1068, which involves local privilege escalation through exploitation of system vulnerabilities. Organizations using affected versions of TrueCrypt, VeraCrypt, or CipherShed face substantial risk of unauthorized data access, particularly in environments with multiple user accounts or shared computing resources. The flaw operates at the kernel level within the Windows operating system, making it particularly dangerous as it can bypass traditional user-mode security controls and access protections.
Mitigation strategies should prioritize immediate patching of affected software versions to the latest releases that contain proper impersonation level validation. System administrators should implement strict access controls and monitor for unauthorized volume access attempts. Additionally, organizations should consider implementing additional security measures such as mandatory access controls, enhanced logging of volume access operations, and regular security assessments of encryption software implementations. The vulnerability highlights the critical importance of proper security token validation in kernel-mode drivers and serves as a reminder of the potential consequences when access control mechanisms fail at the system level.