CVE-2001-1572 in Linux
Summary
by MITRE
The MAC module in Netfilter in Linux kernel 2.4.1 through 2.4.11, when configured to filter based on MAC addresses, allows remote attackers to bypass packet filters via small packets.
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Analysis
by VulDB Data Team • 06/27/2021
The vulnerability described in CVE-2001-1572 represents a critical flaw in the Netfilter framework's MAC address filtering capabilities within Linux kernel versions 2.4.1 through 2.4.11. This issue specifically affects the packet filtering mechanisms that rely on Media Access Control address verification as part of their security posture. The vulnerability resides in the kernel's network packet processing subsystem where MAC address filtering is implemented, creating a potential pathway for unauthorized network access that directly undermines the intended security controls.
The technical implementation flaw occurs when the Netfilter MAC module processes packets that are smaller than the expected minimum packet size required for proper MAC address validation. This condition creates a buffer underflow or improper validation state where the filtering logic fails to properly examine the packet's MAC address information. Attackers can exploit this by crafting and transmitting specially formatted small packets that fall below the minimum size threshold required for the MAC address verification process to function correctly. The vulnerability is classified under CWE-129 as an improper input validation issue, specifically related to insufficient validation of input data size and structure.
From an operational impact perspective, this vulnerability allows remote attackers to bypass network security policies that depend on MAC address filtering as a primary defense mechanism. The attacker can send small packets that are processed without proper MAC address validation, effectively allowing unauthorized traffic to pass through network filters that should have blocked such communications. This creates a significant security risk for networks that rely on MAC address filtering as part of their access control strategy, potentially enabling unauthorized network access, data exfiltration, or further exploitation of network resources. The attack vector is particularly dangerous because it can be executed remotely without requiring local access or authentication credentials.
The exploitation of this vulnerability aligns with techniques documented in the ATT&CK framework under the T1046 tactic for network service scanning and T1562 for evasion techniques. The attack demonstrates how improper input validation can be leveraged to bypass security controls that are fundamental to network defense. Organizations using affected kernel versions face a critical risk where their network segmentation and access control policies may be completely undermined, potentially allowing attackers to establish persistent access to network resources that should remain protected.
Mitigation strategies for this vulnerability include immediate kernel version upgrades to 2.4.12 or later, where the issue has been addressed through proper input validation and size checking mechanisms. Network administrators should also implement additional layers of security controls beyond MAC address filtering, including implementing proper firewall rules, intrusion detection systems, and network segmentation strategies. The vulnerability serves as a reminder of the importance of comprehensive input validation in kernel-level network processing components and highlights the necessity of thorough testing of security features under various edge case conditions to prevent similar issues from occurring in network security implementations.