CVE-2026-71254
Critical
Description
nanoMODBUS through v1.23.0 contains an out-of-bounds write in the Modbus server-side handle_read_file_record function (FC 0x14, Read File Record) in nanomodbus.c. The function validates that the total request size does not exceed 245 bytes and that each sub-request's record_length is at most 124, but it never validates the CUMULATIVE response size across all sub-requests before processing them.
SeverityCritical
CVSS9.8
Exploit probability—
ProductnanoMODBUS
PublishedAug 5, 2026
First seenAug 5, 2026
Weakness typeCWE-787Out-of-bounds write
How to fix
Sources list no fixed version or patch link for this vulnerability.
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| debevv nanoMODBUS | v ≤ 1.23.0 | — |
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