CVE-2018-6856 in SafeGuard Enterprise
Summary
by MITRE
Sophos SafeGuard Enterprise before 8.00.5, SafeGuard Easy before 7.00.3, and SafeGuard LAN Crypt before 3.95.2 are vulnerable to Local Privilege Escalation via IOCTL 0x8020601C. By crafting an input buffer we can control the execution path to the point where a global variable will be written to a user controlled address. We can take advantage of this condition to zero-out the pointer to the security descriptor in the object header of a privileged process or modify the security descriptor itself and run code in the context of a process running as SYSTEM.
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Analysis
by VulDB Data Team • 03/03/2020
The vulnerability described in CVE-2018-6856 represents a critical local privilege escalation flaw affecting multiple Sophos SafeGuard products including SafeGuard Enterprise versions prior to 8.00.5, SafeGuard Easy versions before 7.00.3, and SafeGuard LAN Crypt versions before 3.95.2. This vulnerability resides within the kernel-mode drivers of these security solutions, specifically through an IOCTL (Input/Output Control) command with the identifier 0x8020601C. The flaw stems from insufficient input validation and improper handling of user-supplied data within the driver's processing logic, creating a condition where an attacker can manipulate memory layout to gain elevated privileges.
The technical exploitation of this vulnerability involves crafting a malicious input buffer that allows control over the execution flow within the vulnerable driver. This manipulation leads to the writing of data to a user-controlled memory address through a global variable that should normally be protected. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though the specific mechanism involves heap manipulation and memory pointer control rather than traditional stack corruption. The attacker can leverage this condition to zero out the pointer to the security descriptor within the object header of a privileged process or alternatively modify the security descriptor itself, effectively undermining the security model that protects system processes.
The operational impact of this vulnerability is severe as it enables an attacker with local access to escalate privileges to the SYSTEM level, which represents the highest privilege level in Windows operating systems. This means that any user who can successfully exploit this vulnerability can gain complete control over the affected system, potentially leading to data exfiltration, persistence mechanisms, or further network lateral movement. The attack requires local system access and does not involve network-based exploitation, making it particularly dangerous in environments where local access is possible or where users have elevated privileges through legitimate means. The vulnerability essentially allows for arbitrary code execution in the context of a process running as SYSTEM, providing attackers with unprecedented access to system resources and capabilities.
Mitigation strategies for this vulnerability primarily involve applying the vendor-provided patches and updates for the affected Sophos SafeGuard products. Organizations should prioritize immediate deployment of the security updates released by Sophos to address this privilege escalation flaw. Additionally, system administrators should implement the principle of least privilege and ensure that local user accounts have minimal necessary permissions. The vulnerability aligns with ATT&CK technique T1068 which covers 'Local Privilege Escalation', and specifically targets the execution of malicious code with elevated privileges. Security monitoring should include detection of unusual IOCTL activity patterns and unexpected memory modifications in system processes. Network segmentation and access controls can help limit the potential impact if exploitation occurs, while regular security assessments should verify that all systems running Sophos SafeGuard products are updated to versions that do not contain this vulnerability.