NLnet Labs NSD dname_concatenate() Buffer Overflow Vulnerability [CVE-2019-13207]

CVE number – CVE-2019-13207

dosA vulnerability in NLnet Labs Name Server Daemon (NSD) could allow an unauthenticated, remote attacker to execute arbitrary code or cause a denial of service (DoS) condition on a targeted system.

The vulnerability is due to a stack-based buffer overflow condition that could occur in the dname_concatenate() function, as defined in the dname.c source code file of the affected software. An attacker could exploit this vulnerability by sending crafted requests to the targeted system. A successful exploit could cause the affected application to crash, resulting in a DoS condition, or allow the attacker to execute arbitrary code on the system.

NLnet Labs has confirmed the vulnerability and released software updates.


  • To exploit this vulnerability, the attacker must send crafted requests to the targeted system, making exploitation more difficult in environments that restrict network access from untrusted sources.


  • Administrators are advised to apply the appropriate updates.

    Administrators are advised to allow only trusted users to have network access.

    Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.

    Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.

    Administrators can help protect affected systems from external attacks by using a solid firewall strategy.

    Administrators are advised to monitor affected systems.

Vendor Announcements

  • NLnet Labs has released an issue report at the following link: Issue 20

Fixed Software

  • NLnet Labs has released a software update at the following link: NSD 4.2.2

Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

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