CVE-2009-1086 in ldns
Summary
by MITRE
Heap-based buffer overflow in the ldns_rr_new_frm_str_internal function in ldns 1.4.x allows remote attackers to cause a denial of service (memory corruption) and possibly execute arbitrary code via a DNS resource record (RR) with a long (1) class field (clas variable) and possibly (2) TTL field.
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Analysis
by VulDB Data Team • 09/03/2019
The vulnerability identified as CVE-2009-1086 represents a critical heap-based buffer overflow within the ldns library version 1.4.x, specifically within the ldns_rr_new_frm_str_internal function. This flaw resides in the DNS resource record parsing mechanism that processes DNS responses and queries, making it a significant threat to systems relying on DNS resolution. The vulnerability manifests when the library encounters a malformed DNS resource record containing an excessively long class field, which triggers improper memory handling during the parsing process. The issue stems from inadequate bounds checking mechanisms that fail to validate the length of input data before attempting to allocate memory for the parsed record structure.
The technical exploitation of this vulnerability occurs through the manipulation of DNS resource record fields, particularly targeting the class field and potentially the TTL field. When an attacker crafts a DNS response containing a resource record with an abnormally long class field, the ldns_rr_new_frm_str_internal function attempts to process this data without sufficient validation, leading to memory corruption. The heap-based nature of the overflow indicates that the vulnerability affects dynamically allocated memory regions, potentially allowing attackers to overwrite adjacent memory locations and corrupt the program's heap structure. This type of vulnerability falls under CWE-121, heap-based buffer overflow, which is classified as a severe memory safety issue that can result in arbitrary code execution or system instability.
The operational impact of CVE-2009-1086 extends beyond simple denial of service conditions to potentially enable remote code execution, making it particularly dangerous for systems that process untrusted DNS data. Network infrastructure components, DNS servers, and applications that utilize the ldns library for DNS resolution become vulnerable to attacks that could result in complete system compromise. The vulnerability affects systems where the ldns library is used for DNS parsing, including but not limited to DNS resolvers, DNS forwarders, and applications that handle DNS records from external sources. This makes the attack surface particularly broad as numerous network services and applications rely on DNS functionality for their operations.
Mitigation strategies for this vulnerability require immediate patching of the ldns library to version 1.5.0 or later, which contains the necessary fixes for the buffer overflow conditions. Organizations should implement network monitoring to detect malformed DNS traffic patterns that might indicate exploitation attempts. Additionally, input validation mechanisms should be strengthened at network boundaries to filter out suspicious DNS records before they reach systems utilizing the vulnerable library. The ATT&CK framework categorizes this vulnerability under T1210, Exploitation of Remote Services, and T1059, Command and Scripting Interpreter, as attackers could potentially leverage this flaw to execute arbitrary commands on affected systems. Network segmentation and firewall rules should be configured to limit DNS traffic from untrusted sources, while regular security audits should verify that all systems using DNS functionality have been updated to patched versions of the ldns library.