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Fix off-by-one in TCP MBAP length validation (1-byte OOB write) #123

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Fix off-by-one in TCP MBAP length validation (1-byte OOB write) #123

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2 changes: 1 addition & 1 deletion nanomodbus.c
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Original file line number Diff line number Diff line change
Expand Up @@ -368,7 +368,7 @@ static nmbs_error recv_msg_header(nmbs_t* nmbs, bool* first_byte_received) {
nmbs->msg.unit_id = get_1(nmbs);
nmbs->msg.fc = get_1(nmbs);

if (length < 2 || length > 255)
if (length < 2 || length > 254)
return NMBS_ERROR_INVALID_TCP_MBAP;

// Receive the rest of the message
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