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CVE-2026-71263

Critical

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.

SeverityCritical
CVSS9.1
Exploit probability—
ProductFreeModbus
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

ProductAffected versionsFixed in
cwalter-at FreeModbus0—

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