Vulnerabilities > CVE-2023-22397 - Allocation of Resources Without Limits or Throttling vulnerability in Juniper Junos OS Evolved
Summary
An Allocation of Resources Without Limits or Throttling weakness in the memory management of the Packet Forwarding Engine (PFE) on Juniper Networks Junos OS Evolved PTX10003 Series devices allows an adjacently located attacker who has established certain preconditions and knowledge of the environment to send certain specific genuine packets to begin a Time-of-check Time-of-use (TOCTOU) Race Condition attack which will cause a memory leak to begin. Once this condition begins, and as long as the attacker is able to sustain the offending traffic, a Distributed Denial of Service (DDoS) event occurs. As a DDoS event, the offending packets sent by the attacker will continue to flow from one device to another as long as they are received and processed by any devices, ultimately causing a cascading outage to any vulnerable devices. Devices not vulnerable to the memory leak will process and forward the offending packet(s) to neighboring devices. Due to internal anti-flood security controls and mechanisms reaching their maximum limit of response in the worst-case scenario, all affected Junos OS Evolved devices will reboot in as little as 1.5 days. Reboots to restore services cannot be avoided once the memory leak begins. The device will self-recover after crashing and rebooting. Operator intervention isn't required to restart the device. This issue affects: Juniper Networks Junos OS Evolved on PTX10003: All versions prior to 20.4R3-S4-EVO; 21.3 versions prior to 21.3R3-S1-EVO; 21.4 versions prior to 21.4R2-S2-EVO, 21.4R3-EVO; 22.1 versions prior to 22.1R1-S2-EVO, 22.1R2-EVO; 22.2 versions prior to 22.2R2-EVO. To check memory, customers may VTY to the PFE first then execute the following show statement: show jexpr jtm ingress-main-memory chip 255 | no-more Alternatively one may execute from the RE CLI: request pfe execute target fpc0 command "show jexpr jtm ingress-main-memory chip 255 | no-more" Iteration 1: Example output: Mem type: NH, alloc type: JTM 136776 bytes used (max 138216 bytes used) 911568 bytes available (909312 bytes from free pages) Iteration 2: Example output: Mem type: NH, alloc type: JTM 137288 bytes used (max 138216 bytes used) 911056 bytes available (909312 bytes from free pages) The same can be seen in the CLI below, assuming the scale does not change: show npu memory info Example output: FPC0:NPU16 mem-util-jnh-nh-size 2097152 FPC0:NPU16 mem-util-jnh-nh-allocated 135272 FPC0:NPU16 mem-util-jnh-nh-utilization 6
Vulnerable Configurations
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.