---
id: CVE-2026-11826
title: >-
  OpenPLC_v3 contains a heap-based buffer overflow in the getData() function in
  webserver/core/modbus_master.cpp
summary: >-
  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. I…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-122
published: '2026-07-18'
updated: '2026-07-18'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11826'
references:
  - url: >-
      https://gist.github.com/Shukhrat-03/5cf1825b72e485ef98a32958dfbc611a#security-vulnerability-report
    label: disclosure@vulncheck.com
  - url: 'https://github.com/thiagoralves/OpenPLC_v3'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/thiagoralves/OpenPLC_v3/commit/b4702061dc14d1024856f71b4543298d77007b88
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/openplc-v3-heap-based-buffer-overflow-in-modbus-master-getdata
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-07-19T05:29:21.344Z'
epss: 0.0075
epssPercentile: 0.52994
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.