Buffer overflow in Debevv Nanomodbus
CVE-2026-71254
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.
Vulnerability class: Buffer Overflow
EPSS: 0.003 (23.7th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Debevv Nanomodbus — versions 0
Weakness classification (CWE)
References
- 309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c (third-party-advisory)
- 309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c (third-party-advisory)
Frequently asked questions
- What is CVE-2026-71254?
- CVE-2026-71254 is a critical-severity vulnerability in Debevv Nanomodbus, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2026-08-05.
- How severe is CVE-2026-71254?
- Critical severity. CVSS v3 base score is 9.8 out of 10.