CVE-2026-102762

The `_nx_snmp_utility_object_id_get` function in the NetX Duo SNMP addon does not validate the claimed OID data length against the actual buffer size when the OID uses BER multibyte length encoding, so a remote attacker can send a crafted SNMP packet with a multibyte OID length larger than the available buffer, causing the parser to read past the packet buffer boundary into adjacent heap memory. The OOB bytes are decoded as OID component values and written into the agent's internal OID string buffer, corrupting agent state. On systems with memory protection the OOB read poses the risk of crashing the SNMP agent thread, causing denial of service. On bare metal embedded systems without memory protection the read silently succeeds and corrupts the agent's internal state with heap data.

NetX Duo's WebSocket client resets the unmasking cursor to the first NX_PACKET each time it advances through a chained packet, while the loop's upper bound belongs to the current packet. With the standard contiguous packet-pool layout, a masked server frame split across two packets drives the XOR loop through the first packet's unused payload area and on through the second packet's NX_PACKET control block. The four-byte WebSocket masking key controls the bytes written, so the corruption is attacker-chosen rather than incidental.