Access Control Bypass Vulnerability in NSD by NLnet Labs
CVE-2026-19538

8.2HIGH

Key Information:

Vendor

Nlnet Labs

Status
Nsd
Vendor
CVE Published:
26 August 2026

What is CVE-2026-19538?

An access control list vulnerability in the NSD DNS server allows an attacker to bypass security measures that deny access when connecting over TCP or TLS. This occurs specifically when a query is sent twice on a connection that is kept open, leading to unauthorized access to restricted resources. This vulnerability necessitates prompt remedial action to secure affected systems.

Affected Version(s)

NSD 4.8.0 < 4.15.1

References

https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-19538.txt
vendor-advisory

CVSS V4

Score:
8.2
Severity:
HIGH
Confidentiality:
High
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Qifan Zhang from Palo Alto Networks
.