CVE-2019-1858 in NX-OS
Summary
by MITRE
A vulnerability in the Simple Network Management Protocol (SNMP) input packet processor of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause the SNMP application to leak system memory, which could cause an affected device to restart unexpectedly. The vulnerability is due to improper error handling when processing inbound SNMP packets. An attacker could exploit this vulnerability by sending multiple crafted SNMP packets to an affected device. A successful exploit could allow the attacker to cause the SNMP application to leak system memory because of an improperly handled error condition during packet processing. Over time, this memory leak could cause the SNMP application to restart multiple times, leading to a system-level restart and a denial of service (DoS) condition.
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Analysis
by VulDB Data Team • 09/21/2023
The vulnerability identified as CVE-2019-1858 represents a critical memory management flaw within the Simple Network Management Protocol implementation of Cisco's network operating systems. This weakness exists in both Cisco FXOS Software and Cisco NX-OS Software, affecting a wide range of network infrastructure devices including switches, routers, and network management systems. The vulnerability stems from inadequate error handling mechanisms within the SNMP input packet processor, creating a condition where malformed or specially crafted SNMP packets can trigger unintended system behavior. According to CWE-248, this represents an improper exception handling vulnerability where the system fails to properly manage error conditions during packet processing, leading to resource exhaustion and system instability.
The technical exploitation of this vulnerability occurs through the careful crafting of SNMP packets that trigger specific error conditions within the processing pipeline. When the SNMP application encounters these malformed packets, the improper error handling causes system memory to be allocated but not properly released, resulting in a gradual memory leak. This memory consumption pattern is particularly dangerous because it occurs incrementally over time, making the vulnerability difficult to detect through routine monitoring. The flaw specifically affects the SNMP application's ability to process incoming packets, where the error handling code fails to properly clean up allocated memory resources when encountering unexpected packet structures or invalid data sequences. The vulnerability aligns with ATT&CK technique T1499.004, which describes network denial of service attacks that target system resources to cause service disruption.
The operational impact of CVE-2019-1858 extends beyond simple service disruption to potentially compromise network availability and stability. As memory consumption continues to increase through repeated packet processing, the SNMP application eventually becomes unstable and may restart multiple times, leading to complete system-level restarts. This behavior creates a cascading effect where network management functions become unavailable, potentially causing network administrators to lose visibility into their infrastructure. The vulnerability is particularly concerning in enterprise environments where network devices are expected to maintain continuous operation, as the DoS condition can persist until manual intervention occurs. Network administrators may observe intermittent service disruptions, increased system load, and potential loss of network management capabilities that can affect critical network operations.
Mitigation strategies for CVE-2019-1858 should focus on both immediate defensive measures and long-term architectural improvements. The most effective approach involves applying the vendor-provided security patches and software updates that address the specific memory leak conditions in the SNMP processing code. Organizations should also implement network segmentation and access controls to limit SNMP traffic to trusted management networks, reducing the attack surface. Network monitoring should be enhanced to detect unusual patterns in SNMP packet processing and memory usage trends that could indicate exploitation attempts. Additionally, implementing SNMP version controls and disabling unnecessary SNMP services on network devices can significantly reduce exposure risk. The vulnerability demonstrates the importance of proper input validation and error handling in network infrastructure software, aligning with security best practices outlined in NIST SP 800-128 for network security monitoring and incident response procedures.