CVE-2026-71256 nanoMODBUS Client-Side Out-of-Bounds Read Leading to Wild-Pointer Write via object_id
A remote attacker can trigger a wild-pointer write via an out-of-bounds read in the nanoMODBUS library, potentially leading to code execution or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-71256?
CVE-2026-71256 is a critical memory corruption vulnerability in debevv nanoMODBUS, published on 5 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
nanoMODBUS through v1.23.0 contains an out-of-bounds stack read leading to a wild-pointer write in nmbs_read_device_identification_basic / recv_read_device_identification_res in nanomodbus.c. A fixed 3-element stack array order[3] = {0,1,2} maps object IDs to buffer indices. The server-supplied object_id field (0-255, read directly from the wire) is used without any bounds check as buf_index = order[object_id].
Weakness: CWE-125
Which versions are affected by CVE-2026-71256?
How do I fix CVE-2026-71256?
No fix has been published for CVE-2026-71256 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-2026-71256 being exploited?
There is no known exploitation of CVE-2026-71256 in the wild and no public exploit code.
Sources
Also known as GHSA-vq4c-5vwv-g86v.