fkie_cve-2026-102713

In Eclipse ThreadX NetX Duo versions up to and including 6.5.2.202603, built with packet chaining, the TFTP server does not bound the length of a received DATA datagram. An unauthenticated peer can upload an oversized datagram that writes memory beyond the received packet into the file and read it back by downloading the file, and the same datagram can suspend the server thread permanently.

GHSA-fhxv-gc8j-2f6h

The TFTP server accepts a DATA datagram of any size. The dispatcher rejects datagrams shorter than

four bytes (nxd_tftp_server.c:1037) and nothing anywhere checks an upper bound, in particular not

against the protocol maximum of 4 + NX_TFTP_FILE_TRANSFER_MAX. Two things follow from that one

missing check, both reachable before any authentication because TFTP has none.

The handler passes `nx_packet_length - 4` straight to FileX:

```c

/* addons/tftp/nxd_tftp_server.c:1863, 1889 */

status = nx_packet_copy(packet_ptr, &temp_ptr,

server_ptr -> nx_tftp_server_packet_pool_ptr, NX_WAIT_FOREVER);

...

fx_file_write(&(client_request_ptr -> nx_tftp_client_request_file),

packet_ptr -> nx_packet_prepend_ptr + 4, packet_ptr -> nx_packet_length - 4);

```

`nx_packet_length` is the length of a chain, not of one contiguous buffer, so FileX copies past the

end of the first packet:

```

ERROR: AddressSanitizer: heap-buffer-overflow

READ of size 1280 at 0x621000001108 thread T5

#0 __interceptor_memcpy #1 _fx_utility_memory_copy filex/common/src/fx_utility_memory_copy.c:78

0x621000001108 is 0 bytes to the right of 4104-byte region

```

Those bytes are written into the file the attacker is uploading, and a TFTP read request hands them

back, so this is a memory disclosure with a convenient retrieval channel.

The same datagram also wedges the server. `nx_packet_copy` at :1863 needs…

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fkie_cve-2026-102713

GHSA-fhxv-gc8j-2f6h