CVE-2003-1029 in tcpdump
Summary
by MITRE
The L2TP protocol parser in tcpdump 3.8.1 and earlier allows remote attackers to cause a denial of service (infinite loop and memory consumption) via a packet with invalid data to UDP port 1701, which causes l2tp_avp_print to use a bad length value when calling print_octets.
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Analysis
by VulDB Data Team • 10/12/2024
The vulnerability identified as CVE-2003-1029 represents a critical denial of service flaw in tcpdump versions 3.8.1 and earlier, specifically targeting the Layer 2 Tunneling Protocol (L2TP) implementation within the network packet analyzer. This vulnerability resides in the L2TP protocol parser component of tcpdump, which is widely used for network traffic analysis and monitoring across various operating systems and network environments. The issue manifests when tcpdump processes malformed L2TP packets transmitted over UDP port 1701, which is the standard port for L2TP traffic. The vulnerability stems from inadequate input validation within the protocol parsing logic, creating a scenario where malformed data can trigger unexpected behavior in the packet processing functions.
The technical execution of this vulnerability occurs through a specific code path involving the l2tp_avp_print function, which is responsible for printing L2TP Attribute Value Pairs. When an attacker sends a specially crafted packet containing invalid data to UDP port 1701, the parser encounters a bad length value that causes the print_octets function to be called with malformed parameters. This leads to an infinite loop in the packet processing routine, where the software becomes trapped in a continuous cycle of attempting to process the invalid data. The flaw is classified as a CWE-129 Input Validation and Formatting and relates to CWE-691 Insufficient Control Flow Management, where the control flow becomes unpredictable due to malformed input parameters. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1499.004 Network Denial of Service, where adversaries exploit software flaws to consume system resources and render services unavailable.
The operational impact of this vulnerability extends beyond simple service disruption, as it can consume excessive system resources including CPU cycles and memory allocation, potentially affecting the entire network monitoring infrastructure. When exploited, the vulnerability causes tcpdump to enter an infinite loop that can persist until the system is manually restarted or the process is terminated, effectively rendering the network monitoring capabilities of affected systems unusable. This is particularly concerning in enterprise environments where tcpdump is commonly used for network forensics, intrusion detection, and traffic analysis, as it can compromise the availability of critical network monitoring functions. The vulnerability affects systems running tcpdump versions prior to 3.9.0, making it relevant to a significant portion of network security tooling deployed in the early 2000s. The memory consumption aspect of this vulnerability can lead to system instability and may be exploited by attackers to perform resource exhaustion attacks, potentially affecting other network services running on the same host.
Mitigation strategies for CVE-2003-1029 primarily focus on upgrading tcpdump to version 3.9.0 or later, where the vulnerability has been addressed through improved input validation and proper handling of malformed L2TP packets. System administrators should also implement network segmentation and access control measures to limit exposure to potentially malicious L2TP traffic, particularly on UDP port 1701. Additional defensive measures include deploying network intrusion detection systems that can identify and block malformed L2TP packets, implementing rate limiting on UDP port 1701 traffic, and ensuring that tcpdump is only run on trusted networks or with appropriate privilege restrictions. Organizations should also consider implementing network monitoring solutions that can detect and alert on resource consumption anomalies that may indicate exploitation of this vulnerability. The fix implemented in tcpdump 3.9.0 demonstrates proper error handling and input validation practices that align with secure coding standards and help prevent similar vulnerabilities in network protocol parsers.