CVE-2026-18664
published 2026-08-26CVE-2026-18664: 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…
PriorityP353critical9.1CVSS 3.1
AVNACLPRNUINSUCNIHAH
EPSS
0.33%
26.4th percentile
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
2 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| nlnet_labs | nsd | >= 3.0.0 < 4.15.1 | 4.15.1 |
| nlnetlabs | nsd | >= 3.0.0 < 4.15.1 | 4.15.1 |
CVSS provenance
nvdv3.19.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
nvdv4.08.2HIGHCVSS: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
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Bugzilla
CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison [epel-all]
bugzilla·2026-08-26·CVSS 8.2
CVE-2026-18664 [HIGH] CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison [epel-all]
CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison [epel-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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 c
Bugzilla
CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison
bugzilla·2026-08-26·CVSS 8.2
CVE-2026-18664 [HIGH] CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison
CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison
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.
Bugzilla
CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison [fedora-all]
bugzilla·2026-08-26·CVSS 8.2
CVE-2026-18664 [HIGH] CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison [fedora-all]
CVE-2026-18664 nsd: NSD: Access control bypass due to incorrect IP range comparison [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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
2026-08-26
Published