Wrong interpretation of ACL ranges
Summary
| CVE | CVE-2026-18664 |
|---|---|
| State | PUBLISHED |
| Assigner | NLnet Labs |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-26 09:16:45 UTC |
| Updated | 2026-09-08 20:02:34 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 8.2 HIGH from [email protected]
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.003150000 probability, percentile 0.240310000 (date 2026-09-08)
Problem Types: CWE-284 | CWE-697 | CWE-284 CWE-284 Improper Access Control | CWE-697 CWE-697 Incorrect Comparison
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 8.2 | HIGH | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 8.2 | HIGH | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N |
| 3.1 | [email protected] | Primary | 9.1 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H |
CVSS v4.0 Breakdown
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | NLnet Labs | NSD | affected 3.0.0 4.15.1 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| www.nlnetlabs.nl/downloads/nsd/CVE-2026-18664.txt | [email protected] | www.nlnetlabs.nl | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Qifan Zhang from Palo Alto Networks (en)
CNA: Claude and Ada Logics (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-07-13T21:35:01.000Z | Issue reported by Qifan Zhang |
| CNA | 2026-07-30T13:03:37.000Z | NLnet Labs shares patch |
| CNA | 2026-08-01T08:15:22.000Z | Qifan Zhang verifies patch |
| CNA | 2026-08-26T12:00:00.000Z | Issue reported by Claude and Ada Logics |
| CNA | 2026-08-26T12:00:00.000Z | Fix released with version 4.15.1 |
Solutions
CNA: This issue is fixed in 4.15.1 and all later versions.