A heap buffer overflow is triggered within the TS7Worker::PerformFunctionWrite() routine located in core/s7_server.cpp of the snap7 library. By crafting a specific Modbus packet and sending it to a server running snap7 v1.4.3, an attacker can corrupt heap memory and force the process to terminate. The consequence is a loss of availability for the affected application or device, since the crash requires a restart to resume normal operation.

The vulnerability exists in the snap7 open‑source library maintained by davenardella. Only version 1.4.3 is affected; later releases may contain the fix. Systems employing this library for Modbus communication should be reviewed for potential exposure.

The CVSS score of 6.5 indicates a medium severity, and EPSS data is <1%, showing a low probability of exploitation, but the flaw permits remote exploitation without authentication, enabling an attacker to cause a denial of service. No entry in the CISA KEV catalog suggests the vulnerability has not yet been exploited in the wild, yet the lack of defensive controls means the risk remains significant for exposed services.