CVE-2026-11826 - OpenPLC_v3 Heap-Based Buffer Overflow in Modbus Master getData()

CVE-2026-11826 - OpenPLC_v3 Heap-Based Buffer Overflow in Modbus Master getData()

https://cvefeed.io/rssfeed/latest.atom / Sat, 07/18/2026 - 19:06
CVE ID :CVE-2026-11826
Published : July 18, 2026, 2:17 p.m. | 2 hours, 31 minutes ago
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.
Severity: 8.8 | HIGH
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