An Improper Validation of Syntactic Correctness of Input vulnerability in Packet Forwarding Engine (PFE) of Juniper Networks Junos OS allows an unauthenticated, network-based attacker to cause Denial of Service (DoS).

On all Junos OS MX Series and SRX Series platforms, when SIP ALG is enabled, and a specific SIP packet is received and processed, NAT IP allocation fails for genuine traffic, which causes Denial of Service (DoS). Continuous receipt of this specific SIP ALG packet will cause a sustained DoS condition.

NAT IP usage can be monitored by running the following command.

user@srx> show security nat resource-usage source-pool <source_pool_name>

Pool name: source_pool_name .. Address Factor-index Port-range Used Avail Total Usage X.X.X.X 0 Single Ports 50258 52342 62464 96% <<<<<

• Alg Ports 0 2048 2048 0% This issue affects:

Juniper Networks Junos OS on MX Series and SRX Series

• All versions earlier than 21.2R3-S6;
• 21.3 versions earlier than 21.3R3-S5;
• 21.4 versions earlier than 21.4R3-S5;
• 22.1 versions earlier than 22.1R3-S4;
• 22.2 versions earlier than 22.2R3-S3;
• 22.3 versions earlier than 22.3R3-S1;
• 22.4 versions earlier than 22.4R2-S2, 22.4R3;
• 23.2 versions earlier than 23.2R1-S1, 23.2R2.