Description
OpenPLC_v3 contains a heap-based buffer overflow in the getData() function in webserver/core/modbus_master.cpp. getData() reads characters between two delimiters into a caller-supplied buffer with no size parameter and no bounds check. In parseConfig() the function is invoked with the 100-byte heap-allocated MB_device.dev_name field. An authenticated attacker with access to the OpenPLC web interface can send a crafted HTTP POST to the /modbus endpoint with an oversized device_name value; the value is persisted to mbconfig.cfg and parsed on load, overflowing dev_name and overwriting adjacent struct fields (protocol at offset 108, dev_address at offset 109, ip_port at offset 210). A 200-byte payload writes 100 bytes past the allocation. The result is heap corruption leading to runtime crash and denial of service of the PLC process control loop, with attacker-controlled overwrite of adjacent configuration fields. The upstream repository was archived on 2026-04-04 and no fix is expected; the vendor has confirmed the issue does not affect OpenPLC Runtime v4.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
openplcproject OpenPLC_v3
Default version status: affected
0 to ≤ b470206affected
References
- https://gist.github.com/Shukhrat-03/5cf1825b72e485ef98a32958dfbc611a#security-vulnerability-report ↗
- https://github.com/thiagoralves/OpenPLC_v3/commit/b4702061dc14d1024856f71b4543298d77007b88 ↗
- https://github.com/thiagoralves/OpenPLC_v3 ↗
- https://www.vulncheck.com/advisories/openplc-v3-heap-based-buffer-overflow-in-modbus-master-getdata ↗