CVE-2026-11826 OpenPLC_v3 Heap-Based Buffer Overflow in Modbus Master getData()
An authenticated attacker can cause a heap buffer overflow in OpenPLC_v3 via the web interface, leading to denial of service and configuration corruption.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-11826?
CVE-2026-11826 is a high-severity memory corruption vulnerability in openplcproject OpenPLC_v3, published on 18 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-122
Which versions are affected by CVE-2026-11826?
How do I fix CVE-2026-11826?
No fix has been published for CVE-2026-11826 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-11826 being exploited?
There is no known exploitation of CVE-2026-11826 in the wild and no public exploit code.
Sources
Also known as GHSA-3x22-r5w3-j249.