CVE Catalog

CVE-2026-102715

HighCVSS 7.1
Published: Updated: Translated: NVD NIST

Summary

Heap-buffer-overflow vulnerability in the NX mDNS module. Any host on the LAN can send two mDNS records and cause the responder to write past the end of its transmit packet. The flaw stems from comparing the rounded slot size instead of the actual string length when looking up stored names.

Risk Assessment

An attacker on the same LAN can remotely corrupt neighbouring packets or the pool free list, leading to system instability or potential code execution. The vulnerability is easy to exploit — two ordinary PTR records in response to an _http._tcp query are sufficient.

Recommendation

Update NX to a version containing the fix that compares the slot size against the stored string length or keeps the string length in the slot header. Until the patch is applied, consider restricting mDNS traffic on the LAN.

Related vulnerabilities

Original NVD description (English source)

Any host on the LAN can send two mDNS records and make the responder write past the end of its transmit packet. The string table stores each name in a slot rounded up to a multiple of four: ```c /* addons/mdns/nxd_mdns.c:11436, 11443, 11447 */ memory_len = ((memory_len & 0xFFFFFFFC) + 8) & 0xFFFFFFFF; ... len = *((USHORT*)(p - 2)); /* slot size, not string length */ if ((len == memory_len) && ... _nx_mdns_name_match(start, memory_ptr, memory_size) ...) ``` The lookup that decides whether an incoming name is already stored compares the rounded slot size, so names of 12, 13, 14 and 15 characters share one bucket. A second name in the bucket is answered with the pointer to the first, and the record then carries a string up to three bytes longer than the length the caller accounted for. `_nx_mdns_packet_rr_add` (nxd_mdns.c:8911) sizes its only bound check from that stale length, and `_nx_mdns_name_string_encode` writes the real string. Two PTR records are enough, both ordinary mDNS responses to a `_http._tcp` query, with owner names whose lengths fall in the same bucket: ``` ==87491==ERROR: AddressSanitizer: heap-buffer-overflow WRITE of size 1 at 0x611000000124 thread T5 #0 _nx_mdns_name_string_encode addons/mdns/nxd_mdns.c:13096 #1 _nx_mdns_packet_rr_add addons/mdns/nxd_mdns.c:8911 0x611000000124 is 0 bytes to the right of 228-byte region ``` The overflow is one to three bytes of attacker-influenced name data past `nx_packet_data_end`. In a normal pool that lands in the next packet in the same pool rather than in a redzone, so the visible effect is a corrupted neighbouring packet or a corrupted pool free list rather than a clean crash. Compare the slot size against the stored string length before declaring a match, or keep the string length in the slot header and return it to the caller so the encoder and the bound check agree.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS