CVE-2018-18065 in net-snmp
Summary
by MITRE
_set_key in agent/helpers/table_container.c in Net-SNMP before 5.8 has a NULL Pointer Exception bug that can be used by an authenticated attacker to remotely cause the instance to crash via a crafted UDP packet, resulting in Denial of Service.
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Analysis
by VulDB Data Team • 11/30/2024
The vulnerability identified as CVE-2018-18065 represents a critical null pointer dereference flaw within the Net-SNMP agent's table container helper functionality. This issue exists in the _set_key function located in agent/helpers/table_container.c and affects all versions prior to 5.8 of the Net-SNMP software suite. The vulnerability stems from inadequate input validation and error handling within the SNMP agent's processing pipeline, specifically when handling table container operations that involve key management. Attackers can exploit this weakness by crafting specially formatted UDP packets that trigger the null pointer dereference during normal SNMP processing operations.
The technical exploitation of this vulnerability occurs through authenticated network access to the SNMP agent service, where an attacker can send malformed UDP packets designed to trigger the specific code path containing the null pointer exception. When the Net-SNMP agent processes these crafted packets, the _set_key function fails to properly validate pointer references, leading to a segmentation fault or access violation that causes the SNMP daemon to terminate abruptly. This behavior constitutes a classic denial of service attack vector that can be executed remotely without requiring privileged access beyond network connectivity to the target system. The vulnerability operates at the application layer of the network stack and specifically targets the agent's table container management subsystem.
The operational impact of CVE-2018-18065 extends beyond simple service disruption, as it can be leveraged by attackers to create persistent availability issues within network monitoring infrastructure. Organizations relying on Net-SNMP for network management and monitoring may experience complete loss of SNMP-based monitoring capabilities, potentially masking other security incidents or preventing administrators from detecting network anomalies. The vulnerability is particularly concerning in enterprise environments where SNMP agents are deployed extensively across network infrastructure, as a successful attack could cascade across multiple monitored devices. This issue aligns with CWE-476 which specifically addresses NULL pointer dereference vulnerabilities, and represents a clear violation of the principle of defensive programming that requires proper null checks before pointer operations.
Mitigation strategies for CVE-2018-18065 should prioritize immediate patching of affected Net-SNMP installations to version 5.8 or later, which contains the necessary code fixes to prevent the null pointer dereference condition. Network administrators should also implement additional security controls including SNMP access control lists, restricted UDP port filtering, and monitoring for unusual SNMP traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and error handling in network services, as recommended by the ATT&CK framework's defensive techniques for preventing remote code execution and denial of service conditions. Organizations should also consider implementing network segmentation to limit the exposure of SNMP services to untrusted networks and establish automated monitoring for service availability to detect potential exploitation attempts.