CVE-2021-31364 : Exploit Details and Defense Strategies

A vulnerability designated as CVE-2021-31364 was found in Juniper Networks Junos OS on specific SRX Series platforms. This vulnerability could allow an unauthenticated attacker to send malicious traffic, leading to a Denial of Service (DoS) condition through a crash of the flowd process responsible for traffic forwarding.

Understanding CVE-2021-31364

This vulnerability affects certain Juniper Networks Junos OS versions on SRX Series platforms, potentially causing a crash of critical processes.

What is CVE-2021-31364?

The vulnerability in Juniper Networks Junos OS on SRX Series platforms allows unauthenticated attackers to trigger a crash in the flowd process by sending specific traffic. This results in a Denial of Service (DoS) condition, affecting traffic forwarding on the devices.

The Impact of CVE-2021-31364

The vulnerability poses a medium severity risk, with a CVSS base score of 5.9. While there are no known instances of malicious exploitation, the potential for a sustained DoS condition exists.

Technical Details of CVE-2021-31364

This section delves into the specifics of the vulnerability, including the affected systems and the exploitation mechanism.

Vulnerability Description

An Improper Check for Unusual or Exceptional Conditions combined with a Race Condition in the flow daemon (flowd) of Juniper Networks Junos OS allows attackers to crash essential processes, affecting traffic forwarding.

Affected Systems and Versions

The vulnerability impacts Juniper Networks Junos OS on SRX300 Series, SRX500 Series, SRX1500, and SRX5000 Series with SPC2 running specific versions prior to 20.4R2.

Exploitation Mechanism

The vulnerability can be exploited by unauthenticated network-based attackers by sending specific traffic that triggers a crash in the flowd process, leading to a DoS condition.

Mitigation and Prevention

To address CVE-2021-31364, users should take immediate steps and adopt a security posture that accounts for both short-term and long-term security measures.

Immediate Steps to Take

Remove the session-close log action from policy configurations to mitigate the risk of a crash in the flowd process causing a DoS condition.

Long-Term Security Practices

Regularly update Juniper Networks Junos OS to the patched versions provided by the vendor to prevent exploitation of this vulnerability.

Patching and Updates

Juniper Networks has released patches for this specific issue. Ensure your devices are updated to versions 20.4R2, 21.1R1, or subsequent releases to protect against CVE-2021-31364.