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    2 vulnerabilities by cwalter-at

    CVE-2026-71263 (GCVE-0-2026-71263)

    Vulnerability from nvd – Published: 2026-08-05 12:26 – Updated: 2026-08-05 15:39
    VLAI
    Title
    FreeModbus LINUXTCP Port Off-by-One Global Buffer Overflow in xMBPortTCPPool()
    Summary
    The LINUXTCP port of FreeModbus contains an off-by-one bounds check in xMBPortTCPPool() (demo/LINUXTCP/port/porttcp.c). The check `if (usTCPFrameBytesLeft > MB_TCP_BUF_SIZE)` uses a strict greater-than comparison instead of greater-than-or-equal against the 263-byte MB_TCP_BUF_SIZE limit. An MBAP frame with a Length field of 264 makes usTCPFrameBytesLeft equal to 263, which passes the flawed check, and the subsequent recv() call writes up to 263 bytes starting at buffer offset 7 into the 263-byte static buffer aucTCPBuf, overflowing it by 7 bytes into the adjacent static variable usTCPBufPos. A single crafted, unauthenticated Modbus TCP packet triggers the overflow, since Modbus has no built-in authentication.
    Severity
    9.1 (Critical)
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
    SSVC
    Exploitation: none Automatable: yes Technical Impact: partial
    CISA Coordinator (v2.0.3)
    CWE
    Assigner
    References
    Impacted products
    Vendor Product Version
    cwalter-at FreeModbus Affected: 0 , ≤ * (custom)
    		Create a notification for this product.
    Credits
    Alibek Baxtiyorov
    Show details on NVD website
    To clipboard 

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        "title": "CISA ADP Vulnrichment"
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    ],
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      "title": "FreeModbus LINUXTCP Port Off-by-One Global Buffer Overflow in xMBPortTCPPool()"
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    CVE-2026-71263 (GCVE-0-2026-71263)

    Vulnerability from cvelistv5 – Published: 2026-08-05 12:26 – Updated: 2026-08-05 15:39
    VLAI
    Title
    FreeModbus LINUXTCP Port Off-by-One Global Buffer Overflow in xMBPortTCPPool()
    Summary
    The LINUXTCP port of FreeModbus contains an off-by-one bounds check in xMBPortTCPPool() (demo/LINUXTCP/port/porttcp.c). The check `if (usTCPFrameBytesLeft > MB_TCP_BUF_SIZE)` uses a strict greater-than comparison instead of greater-than-or-equal against the 263-byte MB_TCP_BUF_SIZE limit. An MBAP frame with a Length field of 264 makes usTCPFrameBytesLeft equal to 263, which passes the flawed check, and the subsequent recv() call writes up to 263 bytes starting at buffer offset 7 into the 263-byte static buffer aucTCPBuf, overflowing it by 7 bytes into the adjacent static variable usTCPBufPos. A single crafted, unauthenticated Modbus TCP packet triggers the overflow, since Modbus has no built-in authentication.
    Severity
    9.1 (Critical)
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
    SSVC
    Exploitation: none Automatable: yes Technical Impact: partial
    CISA Coordinator (v2.0.3)
    CWE
    Assigner
    References
    Impacted products
    Vendor Product Version
    cwalter-at FreeModbus Affected: 0 , ≤ * (custom)
    		Create a notification for this product.
    Credits
    Alibek Baxtiyorov
    Show details on NVD website
    To clipboard 

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