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OpenAdvisories
High · 8.2 CVE-2026-18664 EUVD-2026-66347GHSA-fw9f-54cp-j7fc

Wrong interpretation of ACL ranges

Published Aug 26, 2026 · Updated Aug 26, 2026 · Assigned by NLnet Labs

Description

When ranges are used for access control (i.e. of the form 1.2.3.4-1.2.3.25), because NSD wrongly compares the IP address with the range on little endian systems, IPs that were meant to be allowed may be denied, and, IPs that were meant to be denied access could be allowed. An IPv4 address is compared with IPv4 ranges as unsigned 32 bit numbers directly with the endianness of the host, but the values to compare are in network byte order (big-endian). With IPv6 addresses the comparison is done in 4 times a unsigned 32 bit number comparison, again with the endianness of the host where all values are actually in network bye order.

Affected products

VendorProductAffectedFixed
NLnet Labs NSD 3.0.0 – < 4.15.1 4.15.1

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 nsd 4.15.1-1 —
Debian 13 nsd No fix yet —
Debian 12 nsd No fix yet —
ReleasePackageFixed inAdvisory
Ubuntu 26.10 nsd No fix yet —
Show 6 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro 26.04 LTS nsd No fix yet —
Ubuntu Pro 24.04 LTS nsd No fix yet —
Ubuntu Pro 22.04 LTS nsd No fix yet —
Ubuntu Pro 20.04 LTS nsd No fix yet —
Ubuntu Pro 18.04 LTS nsd No fix yet —
Ubuntu Pro 16.04 LTS nsd No fix yet —

Advisories 1

References