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Vulnerability record · CVE-2026-71263 · published 5 August 2026

CVE-2026-71263: Out-of-bounds write vulnerability

The LINUXTCP port of FreeModbus contains an off-by-one bounds check in xMBPortTCPPool (demo/LINUXTCP/port/porttcp.c). The check uses a strict greater-than comparison instead of greater-than-or-equal against the 263-byte MB_TCP_BUF_SIZE limit.

9.1 CVSS 3.1 Critical EPSS 0.50% · top 59.5% CWE-787 · Out-of-bounds write Deferred
9.1CVSS 3.1 base score
0.50%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
26 Aug 2026Last modified by NVD

Description

The LINUXTCP port of FreeModbus contains an off-by-one bounds check in xMBPortTCPPool (demo/LINUXTCP/port/porttcp.c). The check uses a strict greater-than comparison instead of greater-than-or-equal against the 263-byte MB_TCP_BUF_SIZE limit.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

References

LinkTags
https://github.com/cwalter-at/freemodbus
https://github.com/cwalter-at/freemodbus/blob/master/demo/LINUXTCP/port/porttcp.c

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Source: NIST National Vulnerability Database (record CVE-2026-71263), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.