CVE-2026-25823 in Ewon Flexy
Summary
by MITRE • 03/13/2026
HMS Networks Ewon Flexy with firmware before 15.0s4, Cosy+ with firmware 22.xx before 22.1s6, and Cosy+ with firmware 23.xx before 23.0s3 have a stack buffer overflow that leads to a Denial of Service, which can also be exploited to achieve Unauthenticated Remote Code Execution.
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Analysis
by VulDB Data Team • 03/20/2026
The vulnerability identified as CVE-2026-25823 affects HMS Networks Ewon Flexy devices and Cosy+ series products across specific firmware versions, representing a critical security flaw that compromises system integrity and operational availability. This issue manifests as a stack buffer overflow condition within the affected network appliances, specifically targeting the communication protocols and processing routines that handle incoming data requests. The vulnerability resides in the device's firmware implementation where insufficient bounds checking allows maliciously crafted input to overwrite adjacent memory locations on the stack, potentially leading to arbitrary code execution or complete system compromise.
The technical implementation of this flaw enables attackers to exploit the buffer overflow through network-based communication channels without requiring authentication credentials or prior access to the device. The stack buffer overflow occurs when the device processes malformed input data through its network interfaces, particularly affecting HTTP and Modbus protocols commonly used in industrial automation environments. This vulnerability directly maps to CWE-121 Stack-based Buffer Overflow, a well-documented weakness in software development practices where the buffer allocation and memory management fail to properly validate input boundaries. The absence of proper input sanitization and memory protection mechanisms creates an exploitable condition that can be leveraged by threat actors to execute malicious code remotely.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it provides potential for complete system compromise and unauthorized access to industrial control systems. When exploited successfully, the remote code execution capability allows attackers to gain persistent access to the device, potentially enabling them to modify configuration settings, intercept communications, or deploy additional malware within the industrial network environment. The vulnerability affects devices commonly used in critical infrastructure applications including water treatment plants, manufacturing facilities, and energy management systems where uninterrupted operation is essential for safety and operational continuity. The unauthenticated nature of the exploit means that any attacker with network access to the affected devices can potentially compromise them, making this vulnerability particularly dangerous in environments where physical security controls may be insufficient.
Mitigation strategies for CVE-2026-25823 should prioritize immediate firmware updates from HMS Networks to address the stack buffer overflow conditions. Organizations must implement network segmentation and access controls to limit exposure of affected devices to untrusted networks, utilizing firewalls and network access control lists to restrict communication to only necessary endpoints. The implementation of intrusion detection systems can help identify potential exploitation attempts through anomalous network traffic patterns or unusual communication behaviors. Additionally, security monitoring should include regular vulnerability scanning of industrial control systems to identify other potentially unpatched devices within the network infrastructure. According to ATT&CK framework, this vulnerability aligns with T1210 Exploitation of Remote Services and T1059 Command and Scripting Interpreter categories, emphasizing the need for comprehensive defensive measures including network monitoring, access controls, and regular security assessments. Organizations should also consider implementing network traffic analysis tools to detect potential exploitation attempts and establish incident response procedures specifically tailored for industrial control system environments to ensure rapid response to any successful exploitation attempts.