openplcproject OpenPLC 3 Modbus Master modbus_master.cpp getData device_name buffer overflow

Summaryinfo

A vulnerability labeled as problematic has been found in openplcproject OpenPLC 3. The impacted element is the function getData of the file webserver/core/modbus_master.cpp of the component Modbus Master. Executing a manipulation of the argument device_name can lead to buffer overflow. This vulnerability appears as CVE-2026-11826. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in openplcproject OpenPLC 3. It has been declared as problematic. This vulnerability affects the function getData of the file webserver/core/modbus_master.cpp of the component Modbus Master. The manipulation of the argument device_name with an unknown input leads to a buffer overflow vulnerability. The CWE definition for the vulnerability is CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. As an impact it is known to affect integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at gist.github.com. This vulnerability was named CVE-2026-11826 since 06/09/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 07/18/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-45380). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Project Management Software

Vendor

• openplcproject

Name

• OpenPLC

Version

• 3

CPE 2.3info

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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