PatchTheCVECVE-2026-71256: nanoMODBUS through v1.23.0 contains an out-of-bounds stack read leading to a wild-pointer write in nmbs_read_d
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CRITICAL 9.8REMOTE
CVE-2026-71256 is a critical-severity flaw (CVSS 9.8) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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].
Why this priority
- Critical severity
- CISA SSVC: automatable with total technical impact
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.6% (top 55%) |
| CISA exploited list | No |
| Weakness | CWE-125 |
| Published | 2026-08-05 |
| Last modified | 2026-10-23 |
Publisher (CNA): TuranSec
Timeline
- Published CVE record published
- Updated Record last modified
Exact fixes by distribution
Fedora 46 · python-openslide · FIXED · 1.4.7-1.fc46 · FEDORA-2026-336bea884e · source
sudo dnf upgrade --advisory=FEDORA-2026-336bea884e
Fedora ELN · valgrind · FIXED · 3.28.0-1.eln159 · FEDORA-2026-c593ef1d15 · source
sudo dnf upgrade --advisory=FEDORA-2026-c593ef1d15
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Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.