CVE-2014-9402 in C Library
Summary
by MITRE
The nss_dns implementation of getnetbyname in GNU C Library (aka glibc) before 2.21, when the DNS backend in the Name Service Switch configuration is enabled, allows remote attackers to cause a denial of service (infinite loop) by sending a positive answer while a network name is being process.
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Analysis
by VulDB Data Team • 04/16/2022
The vulnerability identified as CVE-2014-9402 resides within the GNU C Library implementation of the Name Service Switch functionality, specifically affecting the nss_dns module responsible for DNS resolution operations. This flaw manifests in glibc versions prior to 2.21 where the getnetbyname function fails to properly handle certain DNS responses, creating a condition that can be exploited by remote attackers to initiate a denial of service attack. The vulnerability is particularly concerning because it operates at the core of system name resolution mechanisms that applications and services rely upon for network communication.
The technical root cause of this vulnerability stems from inadequate input validation within the DNS backend processing logic. When the Name Service Switch configuration is set to utilize the DNS backend, the nss_dns implementation does not properly validate DNS responses received during network name resolution processes. Specifically, when a positive DNS answer is received while a network name is being processed, the implementation enters an infinite loop due to improper state management and response handling. This condition occurs because the code fails to properly terminate the resolution process when encountering certain DNS response patterns, leading to continuous processing of the same response data.
The operational impact of this vulnerability extends beyond simple service disruption as it affects the fundamental network name resolution capabilities of affected systems. Attackers can exploit this weakness by crafting malicious DNS responses that trigger the infinite loop condition, causing the affected system to consume excessive CPU resources and potentially become unresponsive to legitimate network requests. This denial of service condition can affect any application or service that relies on standard glibc name resolution functions, including web servers, database systems, and network management tools. The vulnerability is particularly dangerous in environments where DNS resolution is critical for system operations, as it can cascade into broader service outages.
This vulnerability maps to CWE-835, which describes the weakness of an infinite loop in software implementations. From an adversarial perspective, the attack pattern aligns with techniques described in the MITRE ATT&CK framework under the T1499 category for network denial of service, specifically targeting system and network resources through process consumption. The exploitation requires minimal privileges and can be executed remotely, making it particularly attractive to threat actors seeking to disrupt services without requiring extensive access to target systems. Organizations affected by this vulnerability should prioritize patching their glibc implementations to version 2.21 or later, which includes the necessary fixes to properly handle DNS response validation and prevent the infinite loop condition. Additionally, network monitoring should be implemented to detect unusual DNS traffic patterns that might indicate exploitation attempts, while firewall rules can be configured to limit DNS query responses from untrusted sources to reduce attack surface.