Overview
This report discusses a critical vulnerability, CVE-2024-21595, that affects the Packet Forwarding Engine (PFE) in Juniper Networks Junos OS. The flaw can result in a Denial of Service (DoS), potentially compromising the system and leading to data leakage. The vulnerability affects a range of network devices, making it pertinent to businesses and network administrators alike.
Vulnerability Summary
CVE ID: CVE-2024-21595
Severity: High (CVSS: 7.5)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Denial of service leading to potential system compromise and data leakage.
Affected Products
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Product | Affected Versions
Juniper Networks Junos OS | 21.4R3 versions earlier than 21.4R3-S4
Juniper Networks Junos OS | 22.1R3 versions earlier than 22.1R3-S3
Juniper Networks Junos OS | 22.2R2 versions earlier than 22.2R3-S1
Juniper Networks Junos OS | 22.3 versions earlier than 22.3R2-S2, 22.3R3
Juniper Networks Junos OS | 22.4 versions earlier than 22.4R2
Juniper Networks Junos OS | 23.1 versions earlier than 23.1R2
How the Exploit Works
The vulnerability stems from improper validation of the syntactic correctness of input in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS. An unauthenticated attacker can exploit this flaw by sending a specific type of ICMP traffic at a high rate to a targeted device with VXLAN configured. This action causes a deadlock of the PFE, rendering the device unresponsive and necessitating a manual restart.
Conceptual Example Code
The following is a conceptual shell command that an attacker might use to generate the specific ICMP traffic needed to exploit the vulnerability:
hping3 -1 --flood -a TARGET_IP ATTACKER_IP
In this example, `-1` indicates the ICMP protocol, `–flood` sends packets as fast as possible, `-a TARGET_IP` specifies the target device’s IP address, and `ATTACKER_IP` is the IP of the attacking machine.

