CVE-2021-31369 : Exploit Details and Defense Strategies

A Allocation of Resources Without Limits or Throttling vulnerability in Juniper Networks Junos OS on MX Series platforms with MS-MPC/MS-MIC allows an unauthenticated attacker to cause a partial Denial of Service (DoS) by consuming resources with a high rate of specific traffic.

Understanding CVE-2021-31369

This vulnerability affects Juniper Networks Junos OS on MX Series platforms with specific versions, allowing an unauthenticated attacker to exploit it to cause a partial Denial of Service (DoS).

What is CVE-2021-31369?

CVE-2021-31369 is a vulnerability in Juniper Networks Junos OS that permits an unauthenticated attacker to create a sustained Denial of Service (DoS) condition by abusing the MS-MPC/MS-MIC resources with high-rate specific traffic on MX Series platforms.

The Impact of CVE-2021-31369

The vulnerability could lead to a partial Denial of Service (DoS) where certain traffic consumes resources excessively, causing drops in other processed traffic. If sustained, it can result in a severe denial of service condition.

Technical Details of CVE-2021-31369

The vulnerable configurations involve specific traffic processed by MS-MPC/MS-MIC with attached Class of Service (CoS) rules on service-sets.

Vulnerability Description

The vulnerability allows unauthenticated attackers to exploit the CoS rules and specific traffic processing to create a DoS condition by exhausting resources on MX Series platforms.

Affected Systems and Versions

Juniper Networks Junos OS versions prior to 17.4R3-S5, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S7, 19.3R3-S3, 19.4R3-S5, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3, 20.4R2-S1, 20.4R3, 21.1R1-S1, 21.1R2 are affected.

Exploitation Mechanism

There is no known malicious exploitation of this vulnerability reported.

Mitigation and Prevention

Take immediate steps to mitigate the risk posed by CVE-2021-31369.

Immediate Steps to Take

Update to Juniper Networks Junos OS versions 17.4R3-S5, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S7, 19.3R3-S3, 19.4R3-S5, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3, 20.4R2-S1, 20.4R3, 21.1R1-S1, 21.1R2, 21.2R1, or later.

Long-Term Security Practices

Regularly update software and follow Juniper Networks' security advisories to stay protected against known vulnerabilities.

Patching and Updates

Juniper Networks has released software updates to address CVE-2021-31369. Ensure that all relevant systems are updated with the latest patches.