CVE-2011-1651 in IOS XR
Summary
by MITRE
Cisco IOS XR 3.9.x and 4.0.x before 4.0.3 and 4.1.x before 4.1.1, when an SPA interface processor is installed, allows remote attackers to cause a denial of service (device reload) via a crafted IPv4 packet, aka Bug ID CSCto45095.
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Analysis
by VulDB Data Team • 03/23/2017
The vulnerability described in CVE-2011-1651 represents a critical denial of service flaw affecting Cisco IOS XR software versions 3.9.x and 4.0.x prior to 4.0.3, as well as 4.1.x versions before 4.1.1. This issue specifically impacts network devices equipped with SPA (Service Processor Adapter) interface processors, creating a remote attack vector that can trigger complete device reloads. The vulnerability was identified through Cisco's internal bug tracking system under Bug ID CSCto45095, highlighting the organization's recognition of the severity and impact of this particular flaw in their routing software.
The technical mechanism behind this vulnerability involves the improper handling of crafted IPv4 packets by the affected IOS XR software when operating with SPA interface processors. When such malicious packets are received, the system fails to properly validate or process the packet structure, leading to a condition that causes the device to crash and subsequently reload its operating system. This behavior stems from inadequate input validation within the packet processing routines of the IOS XR kernel, where the software does not sufficiently sanitize incoming IPv4 packet headers or payload data before attempting to process them through the SPA interface processor. The flaw essentially creates a path where malformed packet data can trigger an exception handler that results in system instability and complete device restart.
The operational impact of this vulnerability extends far beyond simple network disruption, as it can compromise the availability of critical network infrastructure components. Network administrators managing devices running affected IOS XR versions face the risk of unauthenticated remote attackers causing service outages that can affect large portions of network traffic, particularly in backbone routers and service provider networks where these devices are commonly deployed. The vulnerability's remote exploitability means that attackers can initiate the denial of service condition without requiring physical access or local network credentials, making it particularly dangerous in environments where network devices are exposed to untrusted traffic. This type of attack can result in significant service degradation, potential data loss during the reload process, and extended network downtime while administrators work to restore affected systems.
Mitigation strategies for this vulnerability require immediate software updates to the affected IOS XR versions, specifically upgrading to 4.0.3 or later for 4.0.x releases and 4.1.1 or later for 4.1.x versions. Organizations should also implement network segmentation and access control measures to limit exposure of affected devices to untrusted traffic sources, while monitoring network traffic for suspicious packet patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-121, which describes buffer overflow conditions, and maps to ATT&CK technique T1499.004, which covers network disruption through resource exhaustion or system crashes. Network security teams should also consider implementing intrusion detection systems that can identify and alert on malformed IPv4 packets that match the characteristics of the exploit, providing additional defense-in-depth measures against this specific vulnerability.