CVE-2021-0206 in Junos
Summary
by MITRE • 01/16/2021
A NULL Pointer Dereference vulnerability in Juniper Networks Junos OS allows an attacker to send a specific packet causing the packet forwarding engine (PFE) to crash and restart, resulting in a Denial of Service (DoS). By continuously sending these specific packets, an attacker can repeatedly disable the PFE causing a sustained Denial of Service (DoS). This issue only affects Juniper Networks NFX Series, SRX Series platforms when SSL Proxy is configured. This issue affects Juniper Networks Junos OS on NFX Series and SRX Series: 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R3-S1; 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3; 19.2 versions prior to 19.2R1-S2, 19.2R2; 19.3 versions prior to 19.3R2. This issue does not affect Juniper Networks Junos OS versions on NFX Series and SRX Series prior to 18.3R1.
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Analysis
by VulDB Data Team • 02/14/2021
The vulnerability described in CVE-2021-0206 represents a critical NULL pointer dereference flaw within Juniper Networks Junos OS operating on specific hardware platforms. This weakness manifests in the packet forwarding engine component of the network infrastructure, specifically affecting NFX Series and SRX Series devices when SSL Proxy functionality is enabled. The flaw stems from inadequate input validation within the processing pipeline that handles specific packet formats, creating a condition where a malicious actor can craft packets that trigger memory access violations. Such vulnerabilities fall under CWE-476 which defines NULL pointer dereference as a common software weakness that can lead to application crashes and system instability.
The technical implementation of this vulnerability exploits the packet forwarding engine's handling of SSL Proxy traffic by sending specially crafted packets that cause the system to attempt to dereference a null pointer during packet processing. When the PFE encounters these malformed packets, it fails to properly validate the incoming data structure, leading to a segmentation fault that results in immediate system crash and automatic restart of the forwarding engine. This behavior creates a cascading effect where the system becomes unavailable for legitimate traffic processing, effectively disabling network functionality. The vulnerability's impact is amplified by the fact that it can be triggered repeatedly, allowing for sustained denial of service attacks that can persist as long as the malicious packets continue to be transmitted.
The operational implications of this vulnerability extend beyond simple service disruption to encompass significant business continuity risks for organizations relying on Juniper networking equipment. Network administrators face the challenge of maintaining availability for critical infrastructure while dealing with potential attacks that can be executed with minimal resources and technical expertise. The specific targeting of SSL Proxy configurations indicates that organizations with secure network traffic inspection capabilities are particularly vulnerable, as this functionality is commonly deployed in enterprise and service provider environments. The vulnerability affects multiple Junos OS versions across different release branches, suggesting a widespread impact that requires coordinated patch management efforts across various network segments.
Mitigation strategies for CVE-2021-0206 should prioritize immediate patch deployment to affected Junos OS versions, with particular attention to the specified release thresholds that address the vulnerability. Network administrators should implement rate limiting and packet filtering mechanisms to prevent the injection of malformed packets into the network infrastructure, while also monitoring for unusual traffic patterns that might indicate exploitation attempts. The ATT&CK framework's T1498 technique for network denial of service provides relevant context for understanding how this vulnerability fits within broader attack patterns targeting network infrastructure availability. Organizations should also consider implementing network segmentation strategies to isolate affected devices and reduce the potential blast radius of successful exploitation attempts, while maintaining detailed logging of network traffic to support incident response activities. The vulnerability's classification as a remote code execution risk through denial of service mechanisms aligns with ATT&CK's approach to categorizing threats based on their potential for system compromise and service disruption.