CVE-2023-36841 Explained : Impact and Mitigation

A vulnerability has been identified in Juniper Networks Junos OS on MX Series, labeled as CVE-2023-36841. This vulnerability could be exploited by an unauthenticated network-based attacker to trigger an infinite loop in the Packet Forwarding Engine (pfe) of Junos OS, leading to a Denial of Service (DoS) condition. The issue arises from an Improper Check for Unusual or Exceptional Conditions affecting interfaces with PPPoE configured and tcp-mss enabled.

Understanding CVE-2023-36841

This section delves into the details of the vulnerability, its impact, technical aspects, and mitigation strategies.

What is CVE-2023-36841?

An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows an attacker to cause a DoS by triggering an infinite loop when sending malformed TCP traffic over an interface configured with PPPoE.

The Impact of CVE-2023-36841

The vulnerability could be exploited by a network-based attacker to cause an infinite loop, consuming all resources on the affected device and requiring a manual restart for recovery.

Technical Details of CVE-2023-36841

The technical aspects of the vulnerability, including the affected systems, versions, and exploitation mechanism, are outlined below:

Vulnerability Description

The vulnerability in Junos OS allows for an infinite loop in the Packet Forwarding Engine, leading to a DoS condition when handling malformed TCP traffic over interfaces with PPPoE configured.

Affected Systems and Versions

Juniper Networks Junos OS on MX Series is impacted by this vulnerability in versions prior to 20.4R3-S7, 21.1R1, 21.2, 21.3, 21.4, 22.1, 22.2, 22.3, and 22.4.

Exploitation Mechanism

The vulnerability can be exploited by sending malformed TCP traffic over a PPPoE-configured interface, triggering an infinite loop in the Packet Forwarding Engine.

Mitigation and Prevention

To address CVE-2023-36841 and mitigate the risks associated with this vulnerability, consider the following steps:

Immediate Steps to Take

Apply the provided software updates: Junos OS 20.4R3-S7, 21.2R3-S6, 21.4R3-S3, 22.1R3-S4, 22.2R3, 22.3R2-S2, 22.3R3, 22.4R2, 23.2R1, and later releases.

Long-Term Security Practices

Regularly update and patch Junos OS to maintain a secure environment.

Patching and Updates

Stay informed about security advisories from Juniper Networks and apply relevant patches promptly.