EUVD-2026-39185
GHSA-27xx-c7vg-hjjj
Severity by source
CVSS:4.0/AV:N/AC:H/AT:N/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
Network-reachable with no auth (the missing client-cert check is the flaw, PR:N); AC:H because it depends on a tls-auth-name config and matching provide-xfr conditions; impact is zone disclosure only (C:H, I:N, A:N).
Primary rating from Vendor (NLnet Labs).
CVSS VectorVendor: NLnet Labs
CVSS:4.0/AV:N/AC:H/AT:N/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
Lifecycle Timeline
2DescriptionCVE.org
When a provide-xfr is given with a tls-auth-name, a secondary requesting a transfer should provide a client certificate with that name. However, no client certificate is needed when the request comes in over TLS over the regular tls-port (and not the tls-auth-port) or over over TCP over the regular port, when the other conditions of the provide-xfr rule match.
AnalysisAI
Zone-transfer authentication bypass in NLnet Labs NSD allows unauthorized secondaries to obtain full zone contents without presenting the required TLS client certificate. Although a provide-xfr rule specifies a tls-auth-name (mandating client-certificate authentication), NSD only enforces this on the dedicated tls-auth-port; requests arriving over plain TCP on the regular port or over TLS on the regular tls-port are served when the remaining provide-xfr conditions match, defeating mutual-TLS access control. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the target NSD to have a provide-xfr rule configured with a tls-auth-name (i.e., XFR-over-TLS client-certificate authentication is in use) - this is not NSD's default and is the core prerequisite. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a credible, prioritizable confidentiality issue rather than a high-score-low-risk artifact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who can reach an NSD server's regular tls-port or plain TCP DNS port - and who meets the provide-xfr rule's other conditions such as a permitted source address - issues an AXFR request without any client certificate and receives the full zone contents that were supposed to be protected by mutual-TLS authentication. No public POC is referenced; AC:H reflects the dependence on a specific tls-auth-name configuration and on satisfying the rule's remaining match conditions. |
| Remediation | Upgrade NSD to the patched release referenced in the NLnet Labs advisory at https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-12490.txt (patch available per vendor advisory; the exact fixed version is not included in the provided data and must be taken from that advisory). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all systems running NLnet Labs NSD and audit secondary nameserver configurations. …
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Remote denial-of-service in NLnet Labs NSD (authoritative DNS name server) version 4.13.0 and later allows an unauthenti
Heap overflow in NLnet Labs NSD allows a malicious or compromised zone primary to corrupt memory on a secondary (slave)
NSD before 4.1.11 allows remote DNS master servers to cause a denial of service (/tmp disk consumption and slave server
Stack buffer overflow in NSD 4.14.0 (NLnet Labs authoritative DNS server) allows a party able to introduce zone data to
query.c in NSD 3.0.x through 3.0.8, 3.1.x through 3.1.1, and 3.2.x before 3.2.12 allows remote attackers to cause a deni
Same technique Authentication Bypass
View allVendor StatusVendor
SUSE
Severity: ImportantShare
External POC / Exploit Code
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