CVE-2026-102715

mDNS string cache accepts a shorter name as a match for a longer stored one, so the known-answer encoder writes past the transmit packet

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Published Sep 29, 2026 CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
Description
In Eclipse ThreadX NetX Duo versions up to and including 6.5.2.202603, the mDNS add-on's string cache accepts a shorter name as a match for a longer stored one. A host on the local link can send two mDNS records that make a device performing continuous service discovery write up to three bytes past its transmit packet, corrupting a neighbouring packet or the pool's free list, and misattribute discovered records.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

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History
Type Values Removed Values Added
Title mDNS string-cache lookup matches on slot size, so a peer name aliases a shorter one and the response encoder writes past the packet mDNS string cache accepts a shorter name as a match for a longer stored one, so the known-answer encoder writes past the transmit packet
Type Values Removed Values Added
Description 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. In Eclipse ThreadX NetX Duo versions up to and including 6.5.2.202603, the mDNS add-on's string cache accepts a shorter name as a match for a longer stored one. A host on the local link can send two mDNS records that make a device performing continuous service discovery write up to three bytes past its transmit packet, corrupting a neighbouring packet or the pool's free list, and misattribute discovered records.
Weaknesses CWE-697
Type Values Removed Values Added
First Time appeared Eclipse
Eclipse threadx Netx Duo
Vendors & Products Eclipse
Eclipse threadx Netx Duo
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}
Type Values Removed Values Added
Description 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.
Title mDNS string-cache lookup matches on slot size, so a peer name aliases a shorter one and the response encoder writes past the packet
Weaknesses CWE-787
References
Metrics cvssV4_0

{'score': 7.1, 'vector': 'CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N'}
Weaknesses

Sources

Status
PUBLISHED
Assigner
eclipse
Published
Updated
Nov 10, 2026, 3:50 PM
Reserved
Sep 29, 2026, 4:15 PM

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Updated
Sep 29, 2026, 6:41 PM

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Status
Awaiting Analysis
Published
Sep 29, 2026, 6:17 PM
Modified
Nov 4, 2026, 2:17 PM

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No data.

Updated
Nov 4, 2026, 3:15 PM

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