CVE-2026-25823
Published: 13 March 2026
Description
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…
more
Unauthenticated Remote Code Execution.
Mitigating Controls (NIST 800-53 r5)AI
Mandates timely identification, reporting, and patching of the stack buffer overflow flaw via firmware updates to versions 15.0s4, 22.1s6, or 23.0s3.
Implements memory protections like stack canaries, ASLR, and DEP to block exploitation of the stack buffer overflow for remote code execution.
Enforces validation of remote network inputs to detect and reject malformed data causing the stack buffer overflow.
Security SummaryAI
CVE-2026-25823 is a stack buffer overflow vulnerability (CWE-121) in HMS Networks' Ewon Flexy and Cosy+ devices. It affects Ewon Flexy with firmware before version 15.0s4, Cosy+ with firmware 22.xx before 22.1s6, and Cosy+ with firmware 23.xx before 23.0s3. The issue enables denial of service and can be further exploited for unauthenticated remote code execution, earning a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).
Remote attackers require no privileges or user interaction to exploit the vulnerability over the network with low complexity. Exploitation can crash affected devices, causing denial of service, or achieve remote code execution, resulting in high impacts to confidentiality, integrity, and availability.
HMS Networks has published a security advisory detailing this and related vulnerabilities in Ewon Flexy and Cosy+ devices, available at https://hmsnetworks.blob.core.windows.net/nlw/docs/default-source/products/cybersecurity/security-advisory/hms-security-advisory-2026-03-09-001---ewon-several-flexy-and-cosy--vulnerabilities.pdf?sfvrsn=f7c027b8_13. Mitigation involves updating to the specified firmware versions: 15.0s4 for Ewon Flexy, 22.1s6 for Cosy+ 22.xx, and 23.0s3 for Cosy+ 23.xx. Additional product information is at https://www.hms-networks.com/p/flexy20500-00ma-ewon-flexy-205.
Details
- CWE(s)
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Stack buffer overflow vulnerability in public-facing HMS Networks Ewon Flexy and Cosy+ devices allows unauthenticated remote code execution over the network, directly enabling T1190: Exploit Public-Facing Application.