Quick answers
- Is CVE-2026-18664 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-18664 being exploited in the wild.
- How severe is CVE-2026-18664?
- Critical severity, with a CVSS score of 9.1, published 26 August 2026.
- Which products and versions are affected?
- NLnet Labs NSD 3.0.0 to 4.15.0.
- Is there a fix for CVE-2026-18664?
- A patch was published on 2026-08-26: NSD 4.15.1 released with fix; patch available for 4.15.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-18664 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-18664?
- Check whether you run Nlnetlabs Nsd. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is an endianness mismatch in IPv4 and IPv6 range comparison logic for access control rules. IPv4 ranges are compared as unsigned 32-bit integers using the host's native endianness, but the values being compared are in network byte order (big-endian), causing incorrect matches on little-endian systems. IPv6 suffers the same issue when comparing four 32-bit values. An attacker can craft IP addresses that bypass intended access restrictions without authentication or special preconditions. The vulnerability affects NSD versions 3.0.0 through 4.15.0; patches are available in version 4.15.1 and as a backport for 4.15.0.
Affected products
- NLnet Labs NSD 3.0.0 to 4.15.0
Timeline
- 2026-08-26: disclosed
- 2026-08-26: patched: NSD 4.15.1 released with fix; patch available for 4.15.0