CVE-2017-3826 in NetFlow Generation Appliance
Summary
by MITRE
A vulnerability in the Stream Control Transmission Protocol (SCTP) decoder of the Cisco NetFlow Generation Appliance (NGA) with software before 1.1(1a) could allow an unauthenticated, remote attacker to cause the device to hang or unexpectedly reload, causing a denial of service (DoS) condition. The vulnerability is due to incomplete validation of SCTP packets being monitored on the NGA data ports. An attacker could exploit this vulnerability by sending malformed SCTP packets on a network that is monitored by an NGA data port. SCTP packets addressed to the IP address of the NGA itself will not trigger this vulnerability. An exploit could allow the attacker to cause the appliance to become unresponsive or reload, causing a DoS condition. User interaction could be needed to recover the device using the reboot command from the CLI. The following Cisco NetFlow Generation Appliances are vulnerable: NGA 3140, NGA 3240, NGA 3340. Cisco Bug IDs: CSCvc83320.
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Analysis
by VulDB Data Team • 08/18/2020
The vulnerability identified as CVE-2017-3826 represents a critical denial of service weakness within Cisco's NetFlow Generation Appliance (NGA) family, specifically affecting devices running software versions prior to 1.1(1a). This flaw resides in the Stream Control Transmission Protocol (SCTP) decoder component responsible for processing network traffic monitoring data on NGA devices. The issue stems from inadequate validation mechanisms within the SCTP packet processing pipeline, creating a scenario where malformed packets can disrupt normal device operations. The vulnerability manifests when SCTP packets are transmitted through monitored network ports, potentially causing complete system hang or unexpected device reloads that result in service interruption. This represents a significant operational risk for organizations relying on continuous network monitoring capabilities provided by these appliances.
The technical exploitation of this vulnerability occurs through the injection of specially crafted malformed SCTP packets into network traffic that flows through the NGA's monitored data ports. The incomplete validation process fails to properly sanitize incoming SCTP packet structures, allowing malformed data to bypass normal processing checks and trigger system instability. The attack vector is particularly concerning as it requires no authentication credentials, making it accessible to remote attackers who can simply send malicious packets to the monitored network segments. However, the vulnerability specifically targets packets transmitted through the NGA's data ports rather than packets directly addressed to the appliance itself, which provides a limited attack surface but maintains significant operational impact. The affected NGA models include the 3140, 3240, and 3340 series, all of which share the same vulnerable software processing logic.
The operational impact of this vulnerability extends beyond simple service disruption, as it can lead to complete network monitoring outages that compromise security infrastructure capabilities. When the NGA device becomes unresponsive or reloads unexpectedly, network flow data collection ceases, potentially leaving organizations without critical visibility into their network traffic patterns and security events. Recovery from such an attack requires manual intervention through the command line interface to execute reboot commands, which introduces additional operational overhead and potential service downtime. This vulnerability directly aligns with CWE-20, which describes improper input validation, and represents a classic example of how protocol decoding flaws can be exploited to achieve denial of service conditions. The attack methodology maps to ATT&CK technique T1499.004, which covers network denial of service attacks, and demonstrates the importance of robust input validation in network security appliances.
Organizations affected by this vulnerability should prioritize immediate software updates to version 1.1(1a) or later to remediate the SCTP packet validation issues. The Cisco advisory recommends implementing network segmentation and access control measures to limit exposure while applying patches, though this approach provides only temporary mitigation. Network administrators should also consider implementing monitoring solutions to detect anomalous SCTP packet patterns that might indicate exploitation attempts. The vulnerability highlights the critical need for thorough protocol validation testing in security appliances, particularly those handling multiple network protocols simultaneously. Additionally, organizations should review their incident response procedures to ensure rapid recovery capabilities when such denial of service conditions occur, as the manual intervention required for device recovery can significantly impact operational continuity and security monitoring effectiveness.