CVE-2017-10621 Explained : Impact and Mitigation

A vulnerability in the telnetd service on Juniper Networks Junos OS has been discovered, potentially allowing remote unauthenticated attackers to cause a denial of service. The affected versions include 12.1X46 prior to 12.1X46-D71, 12.3X48 prior to 12.3X48-D50, 14.1 prior to 14.1R8-S5, 14.1R9, and more.

Understanding CVE-2017-10621

This CVE involves a denial of service vulnerability in the telnetd service on Juniper Networks Junos OS.

What is CVE-2017-10621?

CVE-2017-10621 is a vulnerability in Juniper Networks Junos OS that could be exploited by remote unauthenticated attackers to trigger a denial of service.

The Impact of CVE-2017-10621

The impact of this vulnerability is rated as medium with a CVSS base score of 5.3. It has a low attack complexity and requires no privileges, potentially leading to a denial of service.

Technical Details of CVE-2017-10621

This section provides technical details about the vulnerability.

Vulnerability Description

The vulnerability in the telnetd service on Juniper Networks Junos OS allows remote unauthenticated attackers to cause a denial of service.

Affected Systems and Versions

The following versions of Junos OS are affected:

12.1X46 prior to 12.1X46-D71
12.3X48 prior to 12.3X48-D50
14.1 prior to 14.1R8-S5, 14.1R9
14.1X53 prior to 14.1X53-D50
14.2 prior to 14.2R7-S9, 14.2R8
15.1 prior to 15.1F2-S16, 15.1F5-S7, 15.1F6-S6, 15.1R5-S2, 15.1R6
15.1X49 prior to 15.1X49-D90
15.1X53 prior to 15.1X53-D47
16.1 prior to 16.1R4-S1, 16.1R5
16.2 prior to 16.2R1-S3, 16.2R2

Exploitation Mechanism

The vulnerability can be exploited by remote unauthenticated attackers through the telnetd service on Junos OS.

Mitigation and Prevention

Protect your systems from CVE-2017-10621 with the following steps:

Immediate Steps to Take

Disable the telnet service to completely mitigate the issue.
Reduce the maximum number of connections to a value between 1 and 250.

Long-Term Security Practices

Limit the attack surface of critical infrastructure networking equipment.
Use access lists or firewall filters to restrict access to the device from trusted networks.

Patching and Updates

Ensure your systems are updated with the following software releases to address the vulnerability:

12.1X46-D71, 12.3X48-D50, 14.1R8-S5, 14.1R9, and more.