CVE-2005-4441 in PVLAN protocol
Summary
by MITRE
The PVLAN protocol allows remote attackers to bypass network segmentation and spoof PVLAN traffic via a PVLAN message with a target MAC address that is set to a gateway router, which causes the packet to be sent to the router, where the source MAC is modified, aka "Modification of the MAC spoofing PVLAN jumping attack," as demonstrated by pvlan.c.
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Analysis
by VulDB Data Team • 06/13/2019
The vulnerability described in CVE-2005-4441 represents a critical flaw in Virtual Local Area Network (VLAN) segmentation mechanisms that affects network security protocols. This vulnerability specifically targets the Private VLAN (PVLAN) implementation, which is designed to provide isolation between ports within the same VLAN while maintaining communication capabilities. The flaw allows remote attackers to exploit the PVLAN protocol's handling of destination MAC addresses, enabling them to bypass the intended network segmentation policies.
The technical implementation of this vulnerability stems from improper validation of PVLAN messages, particularly in how the protocol processes target MAC addresses. When an attacker crafts a PVLAN message with a destination MAC address pointing to a gateway router, the network infrastructure incorrectly routes the packet to that router. This misrouting occurs because the PVLAN protocol fails to properly validate that the target MAC address belongs to the appropriate VLAN segment. The vulnerability specifically affects the packet forwarding logic that should maintain PVLAN isolation boundaries, creating a pathway for unauthorized network access.
The operational impact of this vulnerability is significant as it allows attackers to perform MAC address spoofing attacks that effectively bypass network segmentation controls. The attack mechanism described in the CVE involves what is known as a "PVLAN jumping attack," where an attacker can route packets through gateway routers that should normally be inaccessible to certain network segments. This enables unauthorized access to network resources that should be isolated within specific PVLAN zones, potentially allowing attackers to intercept communications, perform man-in-the-middle attacks, or gain access to sensitive network resources. The vulnerability essentially creates a backdoor through which attackers can jump between isolated network segments.
This vulnerability aligns with several cybersecurity frameworks including CWE-284, which addresses improper access control in network protocols, and relates to ATT&CK technique T1046, which covers network service scanning that can lead to privilege escalation through network segmentation bypasses. The attack vector specifically targets the network layer protocol implementation, making it particularly dangerous as it operates below the application layer where many security controls are implemented. Organizations using PVLAN configurations for network segmentation are at risk of having their security boundaries compromised, potentially exposing sensitive data and systems to unauthorized access.
Mitigation strategies for this vulnerability involve implementing proper PVLAN message validation, ensuring that destination MAC addresses are properly validated against the expected VLAN boundaries, and deploying network access control lists that prevent unauthorized routing of PVLAN packets. Network administrators should also consider implementing additional monitoring controls to detect anomalous PVLAN traffic patterns and ensure that gateway routers properly validate source MAC addresses before forwarding packets. The vulnerability demonstrates the importance of proper protocol implementation and validation in maintaining network security boundaries, emphasizing that even well-established protocols like PVLAN require careful attention to edge cases and validation scenarios.