CVE-2020-25171 in V-Server Lite
Summary
by MITRE • 02/20/2021
The affected Fuji Electric V-Server Lite versions prior to 3.3.24.0 are vulnerable to an out-of-bounds write, which may allow an attacker to remotely execute arbitrary code.
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Analysis
by VulDB Data Team • 02/20/2021
Fuji Electric V-Server Lite software, specifically versions preceding the release of version 3.3.24.0, contains a critical memory safety vulnerability classified as an out-of-bounds write. This flaw resides within the application's handling of input data or internal buffer operations, where the software fails to adequately validate the size of incoming requests against the allocated memory boundaries. When an attacker crafts a malicious payload that exceeds the expected limits, the application writes this excess data into adjacent memory locations rather than rejecting the request or truncating the input appropriately. This lack of rigorous boundary checking is a fundamental programming error that compromises the integrity of the program's memory space and creates a pathway for severe security breaches.
The operational impact of this vulnerability is significant due to its potential for remote code execution. An attacker who can interact with the V-Server Lite interface, whether through network services or exposed APIs, can exploit this out-of-bounds write condition to overwrite critical data structures such as function return addresses, exception handlers, or pointers within the heap or stack memory. By carefully controlling these overwritten values, an adversary can redirect the execution flow of the vulnerable process to inject and execute arbitrary machine code. This capability effectively allows full compromise of the underlying operating system hosting the V-Server Lite application, leading to unauthorized access, data exfiltration, or the establishment of persistent backdoors within industrial control systems that rely on this software for automation and monitoring tasks.
From a classification perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-787, which denotes an out-of-bounds write error. This type of flaw is particularly dangerous because it often bypasses standard input validation checks if the developer assumes internal constraints are sufficient without explicit boundary verification. In the context of attack tactics and techniques, exploitation of this vulnerability maps to MITRE ATT&CK technique T1203, which covers Exploitation for Client Execution, or potentially T1059 Command and Scripting Interpreter if the executed code involves scripting languages commonly used in industrial environments. The ability to execute arbitrary code remotely places this flaw in a high-severity category, as it does not require physical access or prior authentication depending on the specific service exposure of the V-Server Lite components.
Mitigation strategies must prioritize immediate patching and network segmentation until updates are applied. Fuji Electric has released version 3.3.24.0 which addresses this memory safety issue by implementing proper bounds checking during buffer operations. Organizations running affected versions should upgrade to this patched release or later as the primary remediation step. In environments where immediate patching is not feasible due to operational constraints, network-level mitigations are essential. This includes restricting access to V-Server Lite services to trusted IP addresses only, utilizing firewalls to block known malicious traffic patterns associated with buffer overflow exploits, and disabling unnecessary network-facing features of the software. Additionally, deploying intrusion detection systems that can identify anomalous memory allocation requests or malformed HTTP packets may provide an additional layer of defense against exploitation attempts while longer-term security hardening measures are implemented.