CVE-2021-0215 in Junos
Summary
by MITRE • 01/16/2021
On Juniper Networks Junos EX series, QFX Series and SRX branch series devices, a memory leak occurs every time the 802.1X authenticator port interface flaps which can lead to other processes, such as the pfex process, responsible for packet forwarding, to crash and restart. An administrator can use the following CLI command to monitor the status of memory consumption: user@device> show task memory detail Please refer to https://kb.juniper.net/KB31522 for details. This issue affects Juniper Networks Junos OS: 14.1X53 versions prior to 14.1X53-D54; 15.1X49 versions prior to 15.1X49-D240 ; 15.1X53 versions prior to 15.1X53-D593; 16.1 versions prior to 16.1R7-S8; 17.2 versions prior to 17.2R3-S4; 17.3 versions prior to 17.3R3-S8; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.1 versions prior to 18.1R3-S10 ; 18.2 versions prior to 18.2R2-S7, 18.2R3-S3; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2; 18.4 versions prior to 18.4R1-S7, 18.4R2-S4, 18.4R3-S2; 19.1 versions prior to 19.1R1-S5, 19.1R2-S2, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S3, 19.3R3; 19.4 versions prior to 19.4R1-S2, 19.4R2. This issue does not affect Juniper Networks Junos OS 12.3, 15.1.
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Analysis
by VulDB Data Team • 02/14/2021
This vulnerability represents a critical memory management flaw within Juniper Networks Junos OS operating on EX series, QFX series, and SRX branch devices. The issue manifests as a persistent memory leak that occurs whenever the 802.1X authenticator port interface experiences flap events, which are common network transitions between up and down states. The vulnerability specifically targets the pfex process responsible for packet forwarding, creating a cascading effect where system stability degrades over time due to progressive memory exhaustion. According to the official Juniper knowledge base article KB31522, administrators can monitor memory consumption using the show task memory detail command, which provides visibility into the memory usage patterns that lead to process crashes.
The technical implementation of this vulnerability stems from inadequate memory deallocation practices within the 802.1X authentication handling code path. Each time an 802.1X port interface flaps, the system fails to properly release allocated memory resources, resulting in a gradual accumulation of memory leaks that eventually overwhelm system resources. This memory leak behavior directly corresponds to CWE-401, which describes improper handling of memory allocation and deallocation, making it particularly dangerous for network infrastructure devices that must maintain continuous operation. The flaw affects multiple Junos OS versions across different release branches, indicating a fundamental issue in the authentication subsystem that was not properly addressed through various maintenance releases.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromising network availability and security posture. When the pfex process crashes and restarts due to memory exhaustion, packet forwarding capabilities are disrupted, leading to potential network outages and service interruptions. Network administrators may experience intermittent connectivity issues as the system attempts to recover from these crashes, while the memory monitoring tools become increasingly important for early detection of the issue. The vulnerability's persistence means that any network environment with active 802.1X authentication will eventually experience system instability, making it particularly concerning for enterprise environments where network reliability is paramount.
Mitigation strategies for this vulnerability require immediate patching of affected Junos OS versions to the recommended secure releases. Organizations should prioritize updating their network infrastructure to versions that contain the memory leak fixes, particularly focusing on the specific version ranges mentioned in the vulnerability description. Network administrators should implement proactive monitoring using the show task memory detail command to detect early signs of memory exhaustion before system crashes occur. Additionally, implementing network segmentation and reducing the frequency of 802.1X port flapping through proper network design can help minimize exposure. From an ATT&CK perspective, this vulnerability represents a potential denial of service vector that could be exploited by adversaries seeking to disrupt network operations, while the memory management flaw aligns with techniques described in the privilege escalation and resource exhaustion domains. The vulnerability also highlights the importance of proper software quality assurance and memory management practices in network infrastructure software development, particularly for critical authentication mechanisms.