CVE-2018-6855 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 0x80202014. By crafting an input buffer we can control the execution path to the point where the constant 0xFFFFFFF 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-2018-6855 represents a critical local privilege escalation flaw affecting multiple Sophos SafeGuard products across different versions. This vulnerability resides in the kernel-mode drivers of the security software, specifically within the handling of IOCTL (Input/Output Control) operations. The flaw manifests through IOCTL code 0x80202014 which processes user-supplied input buffers without adequate validation, creating an exploitable condition that can be leveraged by malicious actors to gain elevated privileges. The vulnerability affects Sophos SafeGuard Enterprise versions prior to 8.00.5, SafeGuard Easy versions prior to 7.00.3, and SafeGuard LAN Crypt versions prior to 3.95.2, indicating a widespread impact across the product line.
The technical exploitation mechanism centers on the manipulation of memory through a crafted input buffer that allows attackers to control execution flow within the kernel driver. Specifically, the vulnerability enables writing the constant value 0xFFFFFFFF to a user-controlled memory address, which represents a critical memory corruption condition. This memory modification directly impacts the SEP_TOKEN_PRIVILEGES structure within the Windows security token object associated with the exploit process. The exploitation technique follows established patterns for privilege escalation attacks where kernel-level memory corruption can be used to modify security token attributes, effectively granting additional privileges to the compromised process. This particular vulnerability maps to CWE-121, which describes stack-based buffer overflow conditions, though the specific implementation involves heap-based memory corruption through improper input validation.
The operational impact of this vulnerability is severe as it allows a local attacker to escalate privileges from standard user level to SYSTEM level execution context. This privilege escalation enables the attacker to interact with and manipulate processes that are normally protected by the operating system's security model. The ability to execute code within the security context of SYSTEM-level processes provides complete control over the affected system, including access to all system resources, user data, and the ability to establish persistent backdoors. The attack requires local system access but does not need network connectivity, making it particularly dangerous in environments where local access is possible. This vulnerability aligns with ATT&CK technique T1068, which describes 'Local Privilege Escalation' and specifically targets the exploitation of kernel-mode vulnerabilities to gain elevated privileges.
The mitigation strategy for CVE-2018-6855 requires immediate patching of affected Sophos SafeGuard products to versions that contain the necessary security fixes. Organizations should prioritize updating all affected systems to the patched versions as soon as possible, with particular attention to systems running the vulnerable software in enterprise environments. System administrators should also implement monitoring for suspicious IOCTL activity and process behavior that might indicate exploitation attempts. Additionally, implementing least privilege principles and restricting local access to systems running vulnerable software can help reduce the attack surface. The vulnerability demonstrates the importance of proper input validation in kernel-mode drivers and highlights the need for comprehensive security testing of device drivers that handle user input. Organizations should also consider implementing behavioral monitoring solutions that can detect anomalous privilege escalation attempts and memory modification patterns that are characteristic of this class of vulnerability.