CVE-2019-0048 in EX4300
Summary
by MITRE
On EX4300 Series switches with TCAM optimization enabled, incoming multicast traffic matches an implicit loopback filter rule first, since it has high priority. This rule is meant for reserved multicast addresses 224.0.0.x, but incorrectly matches on 224.x.x.x. Due to this bug, when a firewall filter is applied on the loopback interface, other firewall filters might stop working for multicast traffic. The command 'show firewall filter' can be used to confirm whether the filter is working. This issue only affects the EX4300 switch. No other products or platforms are affected by this vulnerability. This issue affects: Juniper Networks Junos OS: 14.1X53 versions prior to 14.1X53-D51, 14.1X53-D115 on EX4300 Series; 17.1 versions prior to 17.1R3 on EX4300 Series; 17.2 versions prior to 17.2R3-S2 on EX4300 Series; 17.3 versions prior to 17.3R3-S3 on EX4300 Series; 17.4 versions prior to 17.4R2-S5, 17.4R3 on EX4300 Series; 18.1 versions prior to 18.1R3-S1 on EX4300 Series; 18.2 versions prior to 18.2R2 on EX4300 Series; 18.3 versions prior to 18.3R2 on EX4300 Series.
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Analysis
by VulDB Data Team • 10/24/2023
This vulnerability affects Juniper Networks EX4300 Series switches where Traffic Control Access Matrix (TCAM) optimization is enabled, creating a critical misconfiguration in multicast traffic handling. The flaw stems from an implicit loopback filter rule that incorrectly matches all multicast addresses in the 224.x.x.x range rather than being restricted to the reserved 224.0.0.x addresses as intended. This misclassification occurs due to improper rule prioritization where the high-priority loopback filter intercepts multicast traffic before it can be processed by user-defined firewall filters, effectively bypassing security controls and access policies that should govern such traffic. The issue is classified under CWE-284 Access Control Bypass, representing a fundamental breakdown in network security enforcement mechanisms. According to ATT&CK framework, this vulnerability maps to T1071.004 Application Layer Protocol: DNS and T1046 Network Service Discovery, as it affects network filtering capabilities and can enable unauthorized access to multicast communications.
The technical implementation of this vulnerability exploits the switch's packet processing pipeline where multicast traffic is first evaluated against implicit rules before reaching user-defined filters. When TCAM optimization is active, the switch's hardware-based packet matching system prioritizes the loopback rule, causing all multicast traffic to be processed through this path regardless of the actual multicast address range. This creates a cascading effect where firewall filters applied to the loopback interface become ineffective for multicast traffic, potentially allowing unauthorized multicast communication or preventing legitimate filtering of multicast data streams. The impact extends beyond simple access control as it compromises network segmentation and can lead to information disclosure or denial of service scenarios. Network administrators cannot rely on standard firewall filter configurations to control multicast traffic flow, fundamentally undermining the security posture of affected switches.
The operational impact of CVE-2019-0048 manifests in several critical areas including network security enforcement, traffic management, and compliance monitoring. Organizations relying on multicast traffic for critical applications such as video streaming, voice over IP, or network management protocols face potential security gaps where unauthorized traffic can bypass established security policies. The vulnerability specifically affects multiple Junos OS versions including 14.1X53, 17.1, 17.2, 17.3, 17.4, 18.1, 18.2, and 18.3 releases, with each version requiring specific patch levels to remediate the issue. The affected hardware platform limitation ensures that only EX4300 Series switches are impacted, but this restriction does not diminish the severity of the vulnerability. Network operators must perform comprehensive testing of their firewall configurations after applying patches to ensure that multicast traffic filtering operates correctly and that no security gaps have been introduced during the remediation process.
Mitigation strategies for this vulnerability require immediate patching of affected Junos OS versions with the appropriate security updates provided by Juniper Networks. Organizations should implement comprehensive network monitoring to detect any unusual multicast traffic patterns that might indicate the vulnerability's exploitation. The recommended approach involves verifying firewall filter configurations using the 'show firewall filter' command to ensure that multicast traffic is properly handled according to security policies. Network segmentation strategies should be reviewed and potentially enhanced to compensate for the temporary loss of firewall filter effectiveness during patch deployment. Additionally, network administrators should consider disabling TCAM optimization temporarily if immediate patching is not feasible, though this may impact switch performance. Security teams should conduct vulnerability assessments across their entire Juniper EX4300 deployment to identify and remediate affected devices, while also implementing network traffic analysis to monitor for potential exploitation attempts targeting this specific vulnerability.