CVE-2020-1674 in Junos
Summary
by MITRE • 10/17/2020
Juniper Networks Junos OS and Junos OS Evolved fail to drop/discard delayed MACsec packets (e.g. delayed by more than 2 seconds). Per the specification, called the "bounded receive delay", there should be no replies to delayed MACsec packets. Any MACsec traffic delayed more than 2 seconds should be dropped and late drop counters should increment. Without MACsec delay protection, an attacker could exploit the delay to spoof or decrypt packets. This issue affects: Juniper Networks Junos OS: 16.1 versions prior to 16.1R7-S8; 17.2 versions prior to 17.2R3-S4; 17.3 versions prior to 17.3R3-S8, 17.3R3-S9; 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S5; 18.3 versions prior to 18.3R2-S4, 18.3R3-S3; 18.4 versions prior to 18.4R1-S7, 18.4R2-S5, 18.4R3-S3; 19.1 versions prior to 19.1R3-S2; 19.2 versions prior to 19.2R1-S5, 19.2R3; 19.3 versions prior to 19.3R2-S3, 19.3R3; 19.4 versions prior to 19.4R1-S2, 19.4R2-S1, 19.4R3; 20.1 versions prior to 20.1R1-S2, 20.1R2. Juniper Networks Junos OS Evolved: all versions prior to 19.4R3-EVO; 20.1 versions prior to 20.1R2-EVO. This issue does not affect Junos OS versions prior to 16.1R1.
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Analysis
by VulDB Data Team • 11/20/2020
The vulnerability described in CVE-2020-1674 represents a critical flaw in Juniper Networks Junos OS and Junos OS Evolved implementations that directly impacts the security of MACsec (Media Access Control Security) traffic. This issue stems from the failure to properly enforce bounded receive delay mechanisms, which are fundamental to MACsec protocol specifications designed to prevent replay attacks and ensure packet integrity. The vulnerability specifically affects systems that do not properly drop or discard MACsec packets that arrive with delays exceeding two seconds, creating a window of opportunity for malicious actors to exploit the system's insufficient delay protection mechanisms.
The technical flaw manifests in the absence of proper packet validation and filtering within the MACsec processing pipeline. According to IEEE 802.1AE standards and the MACsec specification, systems must implement bounded receive delay functionality that ensures any MACsec packet arriving with a delay greater than the specified threshold should be immediately dropped and counted in late drop statistics. This mechanism serves as a critical security control that prevents attackers from using packet delay as an attack vector. When this protection fails, the system becomes vulnerable to sophisticated attacks that can manipulate packet timing to bypass security controls, potentially allowing for packet spoofing or decryption attempts.
The operational impact of this vulnerability extends beyond simple packet loss scenarios, creating significant security risks for networks utilizing Juniper devices. Attackers could exploit the delay mechanism to replay previously captured MACsec packets, potentially gaining unauthorized access to network resources or decrypting sensitive information. The vulnerability affects a broad range of Junos OS versions, spanning from 16.1 through 20.1 releases, indicating a widespread exposure across multiple product lines and generations. This extensive scope increases the potential attack surface and makes the vulnerability particularly concerning for organizations with legacy systems or those that have not yet implemented the necessary security patches.
The security implications align with several ATT&CK framework techniques including T1046 Network Service Scanning and T1566 Impairing Defenses, as attackers could leverage this weakness to bypass network security controls. Additionally, this vulnerability maps to CWE-200 Information Exposure, as it potentially exposes network traffic to unauthorized access through the failure of proper security controls. Organizations using affected Junos OS versions face risks of data compromise, network infiltration, and potential denial of service attacks that could disrupt critical network operations. The vulnerability's persistence across multiple OS versions and release branches suggests that many organizations may have been unknowingly exposed to this risk for extended periods.
Mitigation strategies should focus on immediate patching of affected systems to the recommended versions that include proper bounded receive delay implementation. Network administrators must also implement additional monitoring to detect unusual packet delay patterns and potential exploitation attempts. Organizations should conduct comprehensive vulnerability assessments to identify all affected devices and prioritize remediation efforts based on network criticality and exposure levels. The implementation of network segmentation and additional security controls can help reduce the potential impact while patches are deployed. Regular security audits and monitoring of late drop counters should be established to detect any potential exploitation attempts and ensure that the proper MACsec delay protection mechanisms are functioning as intended.