CVE-2026-102721 Memory corruption in NetX Duo
A malicious TFTP server can trigger a heap buffer overflow in the NetX Duo client, leaking adjacent memory or causing a crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-102721?
CVE-2026-102721 is a medium-severity memory corruption vulnerability in Eclipse Foundation NetX Duo, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-125
Which versions are affected by CVE-2026-102721?
How do I fix CVE-2026-102721?
No fix has been published for CVE-2026-102721 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-102721 being exploited?
There is no known exploitation of CVE-2026-102721 in the wild and no public exploit code.
Sources
Also known as GHSA-5cxq-44w6-64mx, GHSA-wvc9-5m9h-rvxc.