Junos OS Evolved: A high rate of specific traffic will cause a complete system outage

An Allocation of Resources Without Limits or Throttling vulnerability in the kernel of Juniper Networks Junos OS Evolved allows an unauthenticated, network-based attacker to cause a Denial of Service (DoS).

If a high rate of specific valid packets are processed by the routing engine (RE) this will lead to a loss of connectivity of the RE with other components of the chassis and thereby a complete and persistent system outage. Please note that a carefully designed lo0 firewall filter will block or limit these packets which should prevent this issue from occurring.

The following log messages can be seen when this issue occurs:

<host> kernel: nf_conntrack: nf_conntrack: table full, dropping packet
This issue affects Juniper Networks Junos OS Evolved:

* All versions earlier than 20.4R3-S7-EVO;
* 21.2R1-EVO and later versions;
* 21.4-EVO versions earlier than 21.4R3-S5-EVO;
* 22.1-EVO versions earlier than 22.1R3-S2-EVO;
* 22.2-EVO versions earlier than 22.2R3-EVO;
* 22.3-EVO versions earlier than 22.3R2-EVO;
* 22.4-EVO versions earlier than 22.4R2-EVO.