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CVE-2026-18664 is an access-control vulnerability in NLnet Labs NSD caused by incorrect interpretation of IPv4 and IPv6 address ranges configured in ACLs on little-endian systems. NSD compares IPv4 addresses as host-endian unsigned 32-bit integers although the address and range values are in network byte order. IPv6 range comparisons similarly perform four host-endian unsigned 32-bit comparisons on network-byte-order values. Consequently, addresses can be evaluated outside their intended ranges: clients meant to be permitted can be denied, while clients meant to be blocked can be permitted.
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No public exploit code observed for this vulnerability.
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12 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An NSD access-control vulnerability on little-endian systems caused by comparing IPv4 and IPv6 address-range values using host endianness even though the values are in network-byte-order (big-endian). This can incorrectly allow denied IP addresses or deny allowed addresses.
A vulnerability affecting the NSD package on FreeBSD; the technical vulnerability type and impact are not specified in the content.
An access-control bypass vulnerability in NSD in which IP range access-control restrictions can be bypassed for unintended IP addresses.
An NSD access-control bypass caused by incorrect IP range comparison, allowing restrictions to be bypassed for unintended IP addresses.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.