EUVD-2026-66349Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/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
AC:H captures the debug-build prerequisite outside attacker control; S:U and A:H reflect child process crash with no confidentiality or integrity impact.
Primary rating from Vendor (NLnet Labs).
CVSS VectorVendor: NLnet Labs
Lifecycle Timeline
3DescriptionCVE.org
Any remote client can crash a (debugging/non-release build type) NSD serve child by sending it a special crafted message with a specially tuned number of DNS Cookie options (17 when UDP payload size is 512). By continuously crashing the serve childs, the remote client can severely hamper or, when positioned sufficiently close, deny all DNS service.
AnalysisAI
NSD authoritative DNS server crashes serve child processes when receiving a crafted DNS message containing exactly 17 DNS Cookie options with a UDP payload size of 512 bytes, triggering a reachable assertion (CWE-617). This condition exists exclusively in debugging and non-release build types - standard production release builds are immune. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The mandatory prerequisite is that NSD must be running as a debug or non-release build - release builds compiled without debug assertions are not vulnerable. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 score of 8.2 (AV:N/AC:L/AT:P/PR:N/UI:N/VA:H) accurately captures the network-accessible, unauthenticated attack vector while the AT:P (Attack Requirements: Present) metric encodes the critical limiting condition - the debug build prerequisite. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | The primary remediation is to ensure NSD is compiled and deployed exclusively as a release build. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, audit all NSD deployments to determine whether production release builds or non-production (debug/non-release) builds are in use-check configuration files, build flags, and vendor documentation. …
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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's proxy protocol port fails to re-evaluate BLOCKED access control list entries on the second DNS query sent over a k
IP range-based access control in NLnet Labs NSD is silently broken on little-endian systems due to an endianness mismatc
Zone-transfer authentication bypass in NLnet Labs NSD allows unauthorized secondaries to obtain full zone contents witho
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
TCP window throttling in NLnet Labs NSD allows any unauthenticated remote attacker to crash individual serve child proce
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 weakness CWE-617 – Reachable Assertion
View allSame technique Denial Of Service
View allShare
External POC / Exploit Code
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