CVE-2026-71255
HIGHCVE-2026-71255 is a high-severity (CVSS 8.6) Out-of-bounds Write vulnerability. O3 Security confirms whether CVE-2026-71255 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
nanoMODBUS through v1.23.0 contains an out-of-bounds write in the Modbus client-side recv_read_device_identification_res() function (FC 0x2B/MEI 0x0E, Read Device Identification) in…
Description
nanoMODBUS through v1.23.0 contains an out-of-bounds write in the Modbus client-side recv_read_device_identification_res() function (FC 0x2B/MEI 0x0E, Read Device Identification) in nanomodbus.c. The server-supplied object_length field (0-246) is validated only against the remaining PDU size (res_size_left) and is never validated against the caller-supplied buffers_length parameter. After copying data with strncpy(buffers_out[buf_index], str, buffers_length), the code unconditionally writes a NUL terminator at buffers_out[buf_index][object_length]. When a malicious or compromised Modbus server sends a response with object_length greater than or equal to the client's buffers_length, this NUL write lands past the end of the caller-provided buffer, corrupting adjacent stack or heap memory on the client.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-71255 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-71255 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-71255. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-71255 in your dependencies?
O3 detects CVE-2026-71255 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.