CVE-2026-102721
NetX TFTP Client Heap Buffer Over-read
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.
INFO
Published Date :
Sept. 29, 2026, 6:17 p.m.
Last Modified :
Sept. 29, 2026, 7:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | MEDIUM | e51fbebd-6053-4e49-959f-1b94eeb69a2c | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Add boundary checks to the error string copy loop.
- Validate buffer pointer against packet boundary.
- Ensure error packets are properly terminated.
- Update TFTP client library.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-102721.
| URL | Resource |
|---|---|
| https://github.com/eclipse-threadx/netxduo/security/advisories/GHSA-wvc9-5m9h-rvxc |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-102721 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-102721
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-102721 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-102721 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Sep. 29, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-102721', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-09-29T18:35:29.043788Z'} -
New CVE Received by [email protected]
Sep. 29, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-125 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/102xxx/CVE-2026-102721.json">CVE-2026-102721</a> Added Reference https://github.com/eclipse-threadx/netxduo/security/advisories/GHSA-wvc9-5m9h-rvxc