CVE-2016-1407 in IOS XR
Summary
by MITRE
Cisco IOS XR through 5.3.2 mishandles Local Packet Transport Services (LPTS) mishandles flow-base entries, which allows remote attackers to cause a denial of service (session drop) by making many connection attempts to open TCP ports, aka Bug ID CSCux95576.
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Analysis
by VulDB Data Team • 08/22/2022
Cisco IOS XR versions through 5.3.2 contain a critical vulnerability in the Local Packet Transport Services (LPTS) component that fundamentally compromises system stability through improper handling of flow-based entries. This vulnerability manifests when the system processes numerous connection attempts targeting open TCP ports, creating a condition where legitimate network sessions become disrupted due to the flawed flow entry management within the LPTS framework. The technical flaw resides in the manner in which the routing platform processes and maintains flow-based entries for packet transport services, specifically failing to properly manage resource allocation when confronted with high-volume connection attempts. This issue directly aligns with CWE-121, which addresses heap-based buffer overflow conditions, and more specifically relates to improper handling of flow state information within network processing modules.
The operational impact of this vulnerability extends beyond simple service disruption, as remote attackers can systematically exploit the flow entry management weakness to cause widespread session drops across affected network infrastructure. When multiple connection attempts are made to open TCP ports, the LPTS component fails to maintain proper flow state tracking, leading to cascading failures where legitimate traffic is dropped or disrupted. This creates a denial of service condition that can affect critical network services and compromise network availability for legitimate users. The attack vector requires only remote access to initiate the exploitation, making it particularly dangerous as it can be executed from external network positions without requiring physical access or elevated privileges within the system.
The vulnerability's exploitation pattern follows established attack methodologies that align with ATT&CK technique T1498, which covers network denial of service attacks. The attacker can repeatedly probe open TCP ports to trigger the flow entry exhaustion condition, causing the system to drop legitimate sessions and potentially leading to complete service unavailability. This particular weakness in the LPTS implementation demonstrates poor resource management and inadequate flow state validation mechanisms within the IOS XR platform's packet processing architecture. The system's inability to properly handle concurrent flow entries under stress conditions creates a predictable failure mode that can be reliably exploited to cause service disruption.
Mitigation strategies for this vulnerability require immediate implementation of software updates from Cisco that address the flow entry handling within LPTS components. Network administrators should also implement traffic rate limiting and connection tracking mechanisms to prevent the exploitation patterns that trigger the vulnerability. The recommended approach includes applying the relevant Cisco security patches that specifically address the flow-based entry management issues in LPTS, along with implementing network access controls that limit the number of connection attempts from any single source. Additionally, monitoring systems should be configured to detect unusual patterns of connection attempts that may indicate exploitation attempts, providing early warning capabilities to prevent successful attacks. Organizations should also consider implementing redundant network paths and failover mechanisms to maintain service availability during potential exploitation events.