CVE-2018-0061 in Junos
Summary
by MITRE
A denial of service vulnerability in the telnetd service on Junos OS allows remote unauthenticated users to cause high CPU usage which may affect system performance. Affected releases are Juniper Networks Junos OS: 12.1X46 versions prior to 12.1X46-D81 on SRX Series; 12.3 versions prior to 12.3R12-S11; 12.3X48 versions prior to 12.3X48-D80 on SRX Series; 15.1 versions prior to 15.1R7; 15.1X49 versions prior to 15.1X49-D150, 15.1X49-D160 on SRX Series; 15.1X53 versions prior to 15.1X53-D59 on EX2300/EX3400 Series; 15.1X53 versions prior to 15.1X53-D68 on QFX10K Series; 15.1X53 versions prior to 15.1X53-D235 on QFX5200/QFX5110 Series; 15.1X53 versions prior to 15.1X53-D495 on NFX Series; 16.1 versions prior to 16.1R4-S12, 16.1R6-S6, 16.1R7; 16.2 versions prior to 16.2R2-S7, 16.2R3; 17.1 versions prior to 17.1R2-S9, 17.1R3; 17.2 versions prior to 17.2R2-S6, 17.2R3; 17.2X75 versions prior to 17.2X75-D100; 17.3 versions prior to 17.3R2-S4, 17.3R3; 17.4 versions prior to 17.4R1-S5, 17.4R2; 18.2X75 versions prior to 18.2X75-D5.
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Analysis
by VulDB Data Team • 05/25/2023
This vulnerability represents a significant denial of service flaw within the telnetd service component of Juniper Networks Junos OS operating systems. The issue manifests as a remote unauthenticated attack vector that can trigger sustained high CPU utilization on affected network devices, effectively degrading system performance and potentially rendering services unavailable. The vulnerability specifically targets the telnet daemon implementation which serves as a legacy remote access mechanism, making it particularly concerning given the widespread deployment of these network appliances in enterprise and service provider environments.
The technical root cause of CVE-2018-0061 lies in improper input validation and handling within the telnetd service when processing certain malformed or crafted network requests. This flaw enables attackers to exploit the service in a way that causes the system to consume excessive computational resources through continuous processing loops or inefficient resource allocation patterns. The vulnerability affects multiple major release series of Junos OS including 12.x, 15.x, 16.x, 17.x, and 18.x versions across various hardware platforms such as SRX Series firewalls, EX2300/EX3400 switches, QFX series switches, and NFX series appliances. The specific version ranges indicate that the issue was present across a broad spectrum of network infrastructure software, suggesting a fundamental flaw in the service implementation rather than a localized bug.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network availability and reliability. When exploited, the high CPU usage can cause the affected device to become unresponsive to legitimate network traffic, effectively creating a denial of service condition that impacts network connectivity and security operations. Network administrators may experience significant challenges in maintaining service levels as the system struggles to process normal network operations while under attack. This vulnerability particularly affects environments where telnet access is enabled and accessible from untrusted networks, making it a critical concern for organizations with legacy network infrastructure deployments. The attack can be executed remotely without authentication credentials, meaning that any system with telnet enabled and accessible to the internet becomes a potential target.
Mitigation strategies for CVE-2018-0061 primarily focus on implementing the official Juniper security patches and firmware updates that address the specific telnetd service vulnerability. Organizations should immediately upgrade their Junos OS installations to the patched versions specified in the security advisories, ensuring that all affected hardware platforms receive the appropriate updates. Network segmentation and access control measures should be implemented to restrict telnet access to trusted administrative networks only, while disabling the telnet service entirely where possible in favor of more secure alternatives such as SSH. Security monitoring should be enhanced to detect unusual CPU utilization patterns that may indicate exploitation attempts, and network access controls should be configured to limit access to telnet services from unauthorized sources. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all instances of affected Junos OS versions across their network infrastructure and prioritize remediation efforts based on risk exposure and business criticality.
This vulnerability aligns with CWE-400 category for unspecified denial of service conditions and demonstrates characteristics consistent with attack patterns documented in the MITRE ATT&CK framework under the service stoppage and resource exhaustion techniques. The remote unauthenticated nature of the attack makes it particularly dangerous as it requires no prior access credentials or network privileges, and the impact affects core network infrastructure services that are fundamental to network operations and security policy enforcement. The widespread impact across multiple Junos OS release series and hardware platforms indicates that this vulnerability represents a systemic flaw in the network device software architecture that required coordinated remediation across the entire Juniper product line.