CVE-2013-1165 in IOS XE
Summary
by MITRE
Cisco IOS XE 2.x and 3.x before 3.4.5S, and 3.5 through 3.7 before 3.7.1S, on 1000 series Aggregation Services Routers (ASR) allows remote attackers to cause a denial of service (card reload) by sending many crafted L2TP packets, aka Bug ID CSCtz23293.
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Analysis
by VulDB Data Team • 05/08/2021
The vulnerability identified as CVE-2013-1165 represents a critical denial of service flaw affecting Cisco IOS XE software versions across multiple releases on the 1000 series Aggregation Services Routers. This vulnerability specifically impacts devices running IOS XE 2.x and 3.x versions prior to 3.4.5S, as well as 3.5 through 3.7 versions before 3.7.1S. The flaw manifests when the affected routers receive a flood of specially crafted Layer 2 Tunneling Protocol packets, leading to a condition where the device must reload its hardware card to recover from the attack. This represents a significant operational risk for network infrastructure, particularly in environments where continuous availability is paramount.
The technical mechanism underlying this vulnerability involves the improper handling of L2TP packets within the IOS XE software implementation. When the router processes these crafted packets, the system fails to properly validate or limit the processing of certain packet attributes, causing the device to enter a state where it repeatedly reloads its line card or processing module. This behavior stems from insufficient input validation and error handling within the L2TP processing subsystem, creating a condition where malicious actors can trigger resource exhaustion or state corruption that ultimately results in the device requiring manual intervention or automatic reload to restore functionality. The vulnerability operates at the network protocol level, specifically targeting the tunneling mechanism used for remote access connections.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network reliability and availability in production environments. Organizations relying on these routers for critical network functions face the risk of unexpected outages that could affect business operations, particularly in scenarios where network redundancy is insufficient or where the device serves as a primary connectivity point for remote users or branch office connections. The requirement for card reload represents a more severe disruption than typical denial of service attacks, as it necessitates hardware-level intervention and can result in extended periods of service unavailability. This vulnerability aligns with CWE-129, Input Validation, and CWE-20, Improper Input Validation, as it demonstrates how inadequate validation of network protocol data can lead to system instability and denial of service conditions.
Mitigation strategies for this vulnerability require immediate software updates to the affected IOS XE versions, specifically upgrading to releases 3.4.5S or 3.7.1S, depending on the current software version in use. Network administrators should also implement traffic filtering mechanisms to limit the number of L2TP packets entering the device and consider rate limiting or packet inspection rules that can identify and drop malformed L2TP traffic. The implementation of network segmentation and access control measures can help reduce exposure by limiting which systems can send L2TP packets to the vulnerable devices. From an operational security perspective, organizations should establish monitoring procedures to detect unusual traffic patterns that might indicate exploitation attempts and maintain detailed incident response procedures for handling device reload events. This vulnerability demonstrates the importance of maintaining up-to-date network device firmware and implementing proper network access controls as outlined in the MITRE ATT&CK framework under the T1499 category for network denial of service attacks.