Software Engineering Institute

Juniper Networks NetScreen firewall products include a Secure Shell version 1 (SSHv1) implementation called Secure Command Shell (SCS). The SSHv1 service contains a remotely exploitable denial-of-service vulnerability.

According to the Juniper Networks Security Advisory:
A malicious person who can connect to the SSHv1 service on a Juniper Networks Netscreen firewall can crash the device before having to authenticate. Upon execution of the attack, the firewall will reboot or hang, which will prevent traffic to flow through the device.

A remote, unauthenticated attacker could cause a denial-of-service condition.

Upgrade

Please refer to the "Recommended Actions" section of the Juniper Networks Advisory for more information on upgrading.

Disable SSHv1

Disable SSHv1 and manage the affected device using another method, such as HTTPS.

Restrict Access

Block or restrict access to the SSHv1 service from untrusted networks, such as the Internet. Juniper Networks also recommends enabling IP Spoof protection to provide additional security.