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CVE-2026-18664— Wrong interpretation of ACL ranges

Quick assessment

Affected
NLnet Labs NSD
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

NLnet Labs NSD是荷兰NLnet Labs组织的一款DNS服务器软件。 NLnet Labs NSD 3.0.0版本至4.15.1之前版本存在安全漏洞，该漏洞源于错误比较IP地址与访问控制范围，可能导致访问控制被绕过，允许本应拒绝的IP地址访问。

CVSS 8.2 · High EPSS 0.26% · P16

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
NLnet Labs NSD 3.0.0< 4.15.1 affected
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I. Basic Information for CVE-2026-18664

Vulnerability Information
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Vulnerability Title
Wrong interpretation of ACL ranges
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
访问控制不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
NLnet Labs NSD 权限许可和访问控制问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
NLnet Labs NSD是荷兰NLnet Labs组织的一款DNS服务器软件。 NLnet Labs NSD 3.0.0版本至4.15.1之前版本存在安全漏洞，该漏洞源于错误比较IP地址与访问控制范围，可能导致访问控制被绕过，允许本应拒绝的IP地址访问。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
NLnet Labs NSD 3.0.0 ~ 4.15.1 -

II. Public POCs for CVE-2026-18664

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III. Intelligence Information for CVE-2026-18664

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Other References for CVE-2026-18664 (1)

Same Patch Batch · NLnet Labs · 2026-08-26 · 4 CVEs total

CVE-2026-19401 8.2 HIGH Remote UDP DoS by sending multiple DNS Cookie options
CVE-2026-19538 8.2 HIGH Bypass of BLOCKED ACL items on proxy protocol port over TCP or TLS
CVE-2026-18916 6.9 MEDIUM Remote TCP DoS by throttling the TCP receive window

IV. Related Vulnerabilities

Same product: NSD
Same vendor: NLnet Labs
Same weakness: CWE-284

V. Comments for CVE-2026-18664

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