Eclipse NetX Duo up to 6.5.1 DHCP Client nxd_dhcp_client.c _nx_dhcp_search_buffer heap-based overflow

Summaryinfo

A vulnerability was found in Eclipse NetX Duo up to 6.5.1 and classified as very critical. This issue affects the function _nx_dhcp_search_buffer of the file addons/dhcp/nxd_dhcp_client.c of the component DHCP Client. Executing a manipulation can lead to heap-based overflow. This vulnerability is handled as CVE-2026-102720. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability has been found in Eclipse NetX Duo up to 6.5.1 and classified as very critical. This vulnerability affects the function _nx_dhcp_search_buffer of the file addons/dhcp/nxd_dhcp_client.c of the component DHCP Client. The manipulation with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

A DHCP server, or anyone on the LAN who answers a DISCOVER first, can make the client read about a kilobyte past the end of the received message. The option walk keeps a pointer and an offset in step, and the only bound check uses the offset: ```c /* addons/dhcp/nxd_dhcp_client.c:7538, 7572 */ while (i < length - 1) { ... size = *(++data); /* data moves 1: type -> length byte */ data += size + 1; /* data moves size + 1 more */ i += size + 1; /* i moves only size + 1 */ } ``` A TLV option occupies size + 2 bytes. `data` is advanced by size + 2 in total, `i` by size + 1, so the offset falls one byte behind the real read position for every option the walk skips. After enough skipped options the check `i < length - 1` still holds while `data` is already past the end of the message, and the subsequent read of the type and length bytes comes from whatever follows. A single OFFER carrying a long run of skippable options is enough: ``` ERROR: AddressSanitizer: heap-buffer-overflow READ of size 1 at 0x61b000000794 thread T5 #0 _nx_dhcp_search_buffer addons/dhcp/nxd_dhcp_client.c:7541 #1 _nx_dhcp_get_option_value addons/dhcp/nxd_dhcp_client.c:7082 0x61b000000794 is located 164 bytes to the right of 1648-byte region ``` A well formed OFFER through the same path is handled normally, the client records the offer and moves to REQUESTING, so the difference is the option layout rather than the harness. The read runs in the DHCP client thread while the client is still unconfigured, so it happens on every boot in reach of a hostile DHCP responder. The values read are used to configure the interface, which is how the disclosed bytes become observable. Advance `i` by size + 2, or derive the bound from `data` rather than keeping a second counter.

The advisory is available at github.com. This vulnerability was named CVE-2026-102720 since 09/29/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/29/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Eclipse

Name

• NetX Duo

Version

• 6.5.0
• 6.5.1

License

• open-source

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