CVE-2004-0649 in l2tpd
Summary
by MITRE
Buffer overflow in write_packet in control.c for l2tpd may allow remote attackers to execute arbitrary code.
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Analysis
by VulDB Data Team • 05/23/2019
The vulnerability identified as CVE-2004-0649 represents a critical buffer overflow flaw within the l2tpd implementation that affects the write_packet function in control.c. This issue arises from insufficient input validation and bounds checking when processing network packets, creating a condition where maliciously crafted data can exceed the allocated buffer space. The vulnerability specifically impacts the Layer 2 Tunneling Protocol daemon which is commonly used for establishing virtual private networks and PPP connections over IP networks. When a remote attacker sends specially crafted packets to a vulnerable l2tpd service, the buffer overflow can be triggered, potentially leading to arbitrary code execution on the affected system.
The technical nature of this flaw aligns with CWE-121, which describes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The vulnerability occurs during packet processing when the write_packet function fails to properly validate the length of incoming data before copying it into a fixed-size buffer. This creates an exploitable condition where an attacker can overwrite return addresses, function pointers, or other critical memory structures, enabling them to redirect program execution flow. The attack vector is remote and requires no authentication, making it particularly dangerous in networked environments where l2tpd services are exposed to untrusted networks.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable full system compromise when exploited successfully. An attacker who successfully exploits this vulnerability can gain arbitrary code execution privileges on the target system, potentially leading to complete system takeover, data exfiltration, or establishment of persistent backdoors. The vulnerability affects systems running vulnerable versions of l2tpd software, particularly those in network infrastructure environments where L2TP services are commonly deployed for remote access and VPN connectivity. Organizations using l2tpd for network connectivity may face significant security risks, especially in environments where the daemon is accessible from untrusted networks or where it serves as a critical network component.
Mitigation strategies for CVE-2004-0649 should prioritize immediate patching of affected l2tpd implementations to address the buffer overflow condition in control.c. System administrators should ensure that all instances of l2tpd are updated to versions that include proper bounds checking and input validation mechanisms. Network segmentation and firewall rules should be implemented to restrict access to l2tpd services only to trusted networks and authorized users. Additionally, monitoring systems should be configured to detect unusual packet patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of input validation and proper memory management practices in network services, aligning with ATT&CK technique T1059 for command and script injection, where successful exploitation would allow an attacker to execute arbitrary commands on the compromised system. Regular security assessments and vulnerability scanning should be conducted to identify and remediate similar buffer overflow conditions in other network services and applications.