CVE-2018-6857 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 0x802022E0. By crafting an input buffer we can control the execution path to the point where the constant 0x12 will be written to a user-controlled address. We can take advantage of this condition to modify the SEP_TOKEN_PRIVILEGES structure of the Token object belonging to the exploit process and grant SE_DEBUG_NAME privilege. This allows the exploit process to interact with higher privileged processes running as SYSTEM and execute code in their security context.
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Analysis
by VulDB Data Team • 03/03/2020
The vulnerability identified as CVE-2018-6857 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 stems from improper input validation within the kernel-mode drivers of these security solutions, specifically when handling IOCTL (Input/Output Control) requests with the identifier 0x802022E0. The flaw exists in the driver's handling of user-supplied input buffers, creating a condition where attacker-controlled data can influence the execution flow of kernel code. The vulnerability manifests through a predictable write operation where a constant value of 0x12 gets written to an address specified by user input, effectively allowing arbitrary memory modification within kernel space. This type of vulnerability is classified under CWE-121 as Stack-based Buffer Overflow, though the specific mechanism involves heap-based memory corruption through improper validation of user-provided data structures. The ATT&CK framework categorizes this as privilege escalation through kernel exploits, specifically leveraging the technique of modifying kernel data structures to gain elevated privileges.
The technical exploitation of this vulnerability relies on the ability to manipulate the SEP_TOKEN_PRIVILEGES structure within the Windows security token management system. When an attacker crafts a malicious input buffer and submits it through the vulnerable IOCTL interface, the kernel driver executes code paths that ultimately result in writing the constant value 0x12 to a memory address controlled by the attacker. This write operation specifically targets the Token object associated with the exploit process, enabling modification of the privilege set stored within the token structure. The value 0x12 corresponds to specific privilege flags within Windows token management, and when properly manipulated, allows the exploitation process to acquire the SE_DEBUG_NAME privilege. This privilege enables the process to debug other processes, including those running with SYSTEM privileges, effectively creating a pathway to execute code within the security context of higher-privileged processes. The vulnerability essentially provides a mechanism to escalate privileges from a standard user account to SYSTEM level access, bypassing normal Windows security controls. The exploitation technique leverages the Windows kernel's token management subsystem and represents a classic example of how improper input validation in kernel drivers can result in complete system compromise.
The operational impact of CVE-2018-6857 is severe and far-reaching within enterprise environments that utilize affected Sophos SafeGuard products. Attackers who successfully exploit this vulnerability can gain SYSTEM-level privileges on compromised systems, effectively providing complete control over the target machine. This privilege escalation allows for unrestricted access to all system resources, including the ability to read and modify any file on the system, modify registry settings, install malicious software, and access sensitive data. The vulnerability is particularly dangerous because it can be exploited locally on a system where an attacker already has user-level access, requiring no network connectivity or remote attack vectors. The exploitation process typically requires minimal privileges to initiate, making it accessible to attackers who may have obtained initial access through other means such as phishing attacks or credential theft. Organizations using affected versions of Sophos SafeGuard products face significant risk, as the vulnerability can be leveraged to establish persistent backdoors, exfiltrate data, or deploy additional malware. The impact extends beyond individual systems to potentially compromise entire enterprise networks, especially when considering that many organizations deploy these security products across their infrastructure. The vulnerability also affects systems where these products are used for endpoint protection, making it particularly concerning for organizations that rely on Sophos SafeGuard for data encryption and security management.
Mitigation strategies for CVE-2018-6857 primarily focus on updating affected Sophos SafeGuard products to versions that contain patches addressing the privilege escalation vulnerability. Organizations should immediately deploy the vendor-supplied updates for SafeGuard Enterprise 8.00.5, SafeGuard Easy 7.00.3, and SafeGuard LAN Crypt 3.95.2 or later versions. Additionally, system administrators should implement network segmentation and access controls to limit potential exploitation vectors, ensuring that only authorized users have access to systems running these vulnerable products. The principle of least privilege should be enforced, limiting user accounts to minimum necessary permissions and restricting local administrative access. Security monitoring should be enhanced to detect suspicious IOCTL activity or unusual privilege escalation attempts within the system. Organizations should also consider implementing endpoint detection and response solutions that can identify exploitation attempts targeting kernel-mode vulnerabilities. The vulnerability highlights the importance of regular security patch management and the need for continuous monitoring of security advisories from software vendors. Furthermore, system administrators should disable unnecessary services and drivers that may expose vulnerable interfaces to potential attackers. Implementing application whitelisting policies can help prevent exploitation by blocking unauthorized executable code from running on systems. The vulnerability also underscores the necessity of proper input validation in kernel-mode drivers and serves as a reminder that even security products can contain exploitable flaws that require careful scrutiny and regular updates to maintain system integrity and protect against sophisticated attacks.