P-Net before 1.0.3 does not check that a complete block header is present in the received data before reading the next block in DCP Set and Identify requests. If the last block ends at the end of the receive buffer, the block length of the following block is read past the end of the buffer. In addition, a DCP Set block with a length smaller than the two-byte block qualifier makes the length underflow, so the block is processed with a length of 65534 bytes. This can cause a crash (denial of service) or disclose a small amount of memory content. Requires ADJACENT network access.