Vulnerabilities > CVE-2018-0239 - Allocation of Resources Without Limits or Throttling vulnerability in Cisco Staros
Attack vector
NETWORK Attack complexity
LOW Privileges required
NONE Confidentiality impact
NONE Integrity impact
NONE Availability impact
PARTIAL Summary
A vulnerability in the egress packet processing functionality of the Cisco StarOS operating system for Cisco Aggregation Services Router (ASR) 5700 Series devices and Virtualized Packet Core (VPC) System Software could allow an unauthenticated, remote attacker to cause an interface on the device to cease forwarding packets. The device may need to be manually reloaded to clear this Interface Forwarding Denial of Service condition. The vulnerability is due to the failure to properly check that the length of a packet to transmit does not exceed the maximum supported length of the network interface card (NIC). An attacker could exploit this vulnerability by sending a crafted IP packet or a series of crafted IP fragments through an interface on the targeted device. A successful exploit could allow the attacker to cause the network interface to cease forwarding packets. This vulnerability could be triggered by either IPv4 or IPv6 network traffic. This vulnerability affects the following Cisco products when they are running the StarOS operating system and a virtual interface card is installed on the device: Aggregation Services Router (ASR) 5700 Series, Virtualized Packet Core-Distributed Instance (VPC-DI) System Software, Virtualized Packet Core-Single Instance (VPC-SI) System Software. Cisco Bug IDs: CSCvf32385.
Vulnerable Configurations
| Part | Description | Count |
|---|---|---|
| OS | 5 | |
| Hardware | 1 |
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Locate and Exploit Test APIs An attacker exploits a sample, demonstration, or test API that is insecure by default and should not be resident on production systems. Some applications include APIs that are intended to allow an administrator to test and refine their domain. These APIs should usually be disabled once a system enters a production environment. Testing APIs may expose a great deal of diagnostic information intended to aid an administrator, but which can also be used by an attacker to further refine their attack. Moreover, testing APIs may not have adequate security controls or may not have undergone rigorous testing since they were not intended for use in production environments. As such, they may have many flaws and vulnerabilities that would allow an attacker to severely disrupt a target.
- Flooding An attacker consumes the resources of a target by rapidly engaging in a large number of interactions with the target. This type of attack generally exposes a weakness in rate limiting or flow control in management of interactions. Since each request consumes some of the target's resources, if a sufficiently large number of requests must be processed at the same time then the target's resources can be exhausted. The degree to which the attack is successful depends upon the volume of requests in relation to the amount of the resource the target has access to, and other mitigating circumstances such as the target's ability to shift load or acquired additional resources to deal with the depletion. The more protected the resource and the greater the quantity of it that must be consumed, the more resources the attacker may need to have at their disposal. A typical TCP/IP flooding attack is a Distributed Denial-of-Service attack where many machines simultaneously make a large number of requests to a target. Against a target with strong defenses and a large pool of resources, many tens of thousands of attacking machines may be required. When successful this attack prevents legitimate users from accessing the service and can cause the target to crash. This attack differs from resource depletion through leaks or allocations in that the latter attacks do not rely on the volume of requests made to the target but instead focus on manipulation of the target's operations. The key factor in a flooding attack is the number of requests the attacker can make in a given period of time. The greater this number, the more likely an attack is to succeed against a given target.
- Excessive Allocation An attacker causes the target to allocate excessive resources to servicing the attackers' request, thereby reducing the resources available for legitimate services and degrading or denying services. Usually, this attack focuses on memory allocation, but any finite resource on the target could be the attacked, including bandwidth, processing cycles, or other resources. This attack does not attempt to force this allocation through a large number of requests (that would be Resource Depletion through Flooding) but instead uses one or a small number of requests that are carefully formatted to force the target to allocate excessive resources to service this request(s). Often this attack takes advantage of a bug in the target to cause the target to allocate resources vastly beyond what would be needed for a normal request. For example, using an Integer Attack, the attacker could cause a variable that controls allocation for a request to hold an excessively large value. Excessive allocation of resources can render a service degraded or unavailable to legitimate users and can even lead to crashing of the target.
- XML Ping of the Death An attacker initiates a resource depletion attack where a large number of small XML messages are delivered at a sufficiently rapid rate to cause a denial of service or crash of the target. Transactions such as repetitive SOAP transactions can deplete resources faster than a simple flooding attack because of the additional resources used by the SOAP protocol and the resources necessary to process SOAP messages. The transactions used are immaterial as long as they cause resource utilization on the target. In other words, this is a normal flooding attack augmented by using messages that will require extra processing on the target.
- XML Entity Expansion An attacker submits an XML document to a target application where the XML document uses nested entity expansion to produce an excessively large output XML. XML allows the definition of macro-like structures that can be used to simplify the creation of complex structures. However, this capability can be abused to create excessive demands on a processor's CPU and memory. A small number of nested expansions can result in an exponential growth in demands on memory.
Nessus
| NASL family | CISCO |
| NASL id | CISCO-SA-20180418-STAROS.NASL |
| description | According to its self-reported version and model number, the remote Cisco ASR device is affected by a denial of service vulnerability. Please see the included Cisco BID and the Cisco Security Advisory for more information. |
| last seen | 2020-06-01 |
| modified | 2020-06-02 |
| plugin id | 109400 |
| published | 2018-04-27 |
| reporter | This script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof. |
| source | https://www.tenable.com/plugins/nessus/109400 |
| title | Cisco ASR StarOS Interface Forwarding Denial of Service Vulnerability (cisco-sa-20180418-staros) |
| code | |