CVE-2019-13207 in nsd
Summary
by MITRE
nsd-checkzone in NLnet Labs NSD 4.2.0 has a Stack-based Buffer Overflow in the dname_concatenate() function in dname.c.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 10/17/2023
The vulnerability identified as CVE-2019-13207 represents a critical stack-based buffer overflow flaw within the nsd-checkzone utility of NLnet Labs NSD version 4.2.0. This issue resides in the dname_concatenate() function located in the dname.c source file, fundamentally compromising the integrity of the DNS server software's validation mechanisms. The flaw manifests when processing malformed DNS domain name data structures, specifically affecting the way the system handles domain name concatenation operations during DNS zone file validation processes. This vulnerability directly impacts the security posture of DNS infrastructure deployments that rely on NSD's zone checking capabilities, potentially allowing attackers to exploit memory corruption during validation procedures.
The technical execution of this buffer overflow occurs through improper bounds checking within the dname_concatenate() function, where the system fails to adequately validate the length of domain name data being processed. When nsd-checkzone encounters specially crafted domain name structures, the function attempts to concatenate domain name components without sufficient buffer size verification, leading to memory corruption on the stack. This condition creates an exploitable scenario where an attacker can manipulate input data to overflow adjacent stack memory regions, potentially enabling arbitrary code execution or denial of service conditions. The vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue that has been consistently identified as a high-risk vulnerability across multiple security frameworks and standards.
The operational impact of CVE-2019-13207 extends beyond simple denial of service scenarios, as it can potentially allow remote attackers to execute arbitrary code on systems running vulnerable versions of NSD. This risk is particularly concerning for DNS infrastructure administrators who rely on nsd-checkzone for routine zone validation and monitoring tasks, as the utility may be invoked automatically or through automated processes. The vulnerability can be exploited through maliciously crafted DNS zone files that contain oversized or malformed domain name records, making it possible for attackers to compromise systems during routine administrative operations or through indirect attack vectors that leverage the zone validation functionality. Organizations using NSD 4.2.0 should consider this vulnerability as a potential entry point for advanced persistent threats, particularly in environments where DNS servers handle untrusted input from external sources.
Mitigation strategies for this vulnerability require immediate patching of affected NSD installations to version 4.2.1 or later, which contains the necessary fixes for the buffer overflow condition. System administrators should also implement input validation measures that restrict the size and format of DNS zone files processed by nsd-checkzone, particularly when dealing with external or untrusted data sources. Network segmentation and access controls should be strengthened to limit who can submit or modify DNS zone files that would be processed by the vulnerable utility. The remediation process should include thorough testing of patched systems to ensure that the vulnerability has been fully resolved without introducing regressions in DNS service functionality. Additionally, security monitoring should be enhanced to detect potential exploitation attempts through unusual patterns in DNS zone validation activities, as outlined in the ATT&CK framework's techniques for command and control communications and privilege escalation through software exploitation.