A TFTP server that answers with a short ERROR packet makes the client read up to 64 bytes past the
received datagram.
Each receive path checks only that the datagram is at least four bytes long (nxd_tftp_client.c:1229,
1521, 1984). When the opcode is NX_TFTP_CODE_ERROR the message string is copied with a loop whose
only limits are the destination buffer and a NUL byte:
```c
/* addons/tftp/nxd_tftp_client.c:1769 */
for (i = 0; (i < (sizeof(tftp_client_ptr -> nx_tftp_client_error_string) - 1)) && (*buffer_ptr); i++)
```
Nothing compares `buffer_ptr` against `nx_packet_append_ptr`. An ERROR packet that carries no
terminating NUL, which a server controls completely, walks the loop off the end of the packet until
it happens to meet a zero byte or fills the 64 byte destination.
```
ERROR: AddressSanitizer: heap-buffer-overflow
READ of size 1 at 0x60d0000000c8 thread T4
#0 _nxd_tftp_client_file_read addons/tftp/nxd_tftp_client.c:1769
0x60d0000000c8 is 0 bytes to the right of 136-byte region
```
The open path has the same loop at :1327 and reports the same way. What is read lands in
`nx_tftp_client_error_string`, which the application is expected to display or log, so adjacent
packet pool memory ends up in whatever the device does with the error text.
Add `(buffer_ptr < packet_ptr -> nx_packet_append_ptr)` to the loop condition in all three paths.
CVSS
No CVSS.
References
Configurations
No configuration.
History
29 Sep 2026, 18:17
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-09-29 18:17
Updated : 2026-09-29 19:17
NVD link : CVE-2026-102721
Mitre link : CVE-2026-102721
CVE.ORG link : CVE-2026-102721
JSON object : View
Products Affected
No product.
CWE
CWE-125
Out-of-bounds Read