Improper access control in NSD - CVE-2026-12490
Published: June 25, 2026
Vulnerability identifier: #VU135157
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-12490
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: NLnet Labs
Affected software:
NSD
NSD
Detailed vulnerability description
The vulnerability allows a remote user to bypass client certificate-based access controls for zone transfers.
The vulnerability exists due to improper access control in the provide-xfr zone transfer authorization logic when handling zone transfer requests over the regular tls-port or regular TCP port. A remote user can request a zone transfer without presenting the required client certificate to bypass client certificate-based access controls for zone transfers.
Exploitation requires matching the other access control conditions of the provide-xfr rule, and the issue applies when tls-auth-xfr-only is not explicitly set to yes.
How to mitigate CVE-2026-12490
Install security update from vendor's website.