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
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| 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.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | nsd | 4.15.1-1 | — |
| Debian 13 | nsd | No fix yet | — |
| Debian 12 | nsd | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | nsd | No fix yet | — |
Show 6 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| 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
- WID-SEC-2026-3663 OpenBSD: Mehrere Schwachstellen BSI CERT-Bund (WID) · Sep 29, 2026
References
- https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-18664.txt vendor-advisory