CVE-2002-0403 in Ethereal
Summary
by MITRE
DNS dissector in Ethereal before 0.9.3 allows remote attackers to cause a denial of service (CPU consumption) via a malformed packet that causes Ethereal to enter an infinite loop.
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Analysis
by VulDB Data Team • 06/27/2021
The vulnerability identified as CVE-2002-0403 represents a critical denial of service flaw within the DNS dissector component of Ethereal network protocol analyzer version 0.9.2 and earlier. This vulnerability specifically targets the packet parsing logic that handles Domain Name System traffic analysis, creating a scenario where malformed DNS packets can trigger infinite loop conditions within the application's processing engine. The flaw exists in the way Ethereal handles certain edge cases in DNS packet structures, particularly those involving malformed resource record data that causes the dissector to continuously iterate through processing loops without proper termination conditions. The vulnerability operates at the application layer and affects the network protocol analysis functionality rather than the underlying network stack itself.
The technical implementation of this vulnerability stems from inadequate input validation and error handling within the DNS dissector module. When Ethereal encounters a malformed DNS packet containing specific sequence patterns or invalid record structures, the dissector enters a recursive or iterative processing loop that consumes excessive CPU resources. This behavior is classified as a resource exhaustion attack vector where the attacker can cause the application to become unresponsive or consume 100% CPU cycles indefinitely. The flaw is particularly dangerous because DNS traffic is ubiquitous in network environments, making it trivial for remote attackers to exploit this vulnerability by simply sending maliciously crafted DNS packets to a target system running the vulnerable version of Ethereal.
The operational impact of CVE-2002-0403 extends beyond simple service disruption to potentially compromise network monitoring capabilities and system availability. Network administrators relying on Ethereal for traffic analysis and troubleshooting would experience complete loss of functionality when this vulnerability is exploited, as the application becomes unresponsive and unable to process any further network packets. This creates a cascading effect where legitimate network monitoring activities are disrupted, potentially masking actual security incidents or network issues that would otherwise be detected through normal protocol analysis. The vulnerability affects both local and remote attack scenarios, as any system running the vulnerable Ethereal version is susceptible to exploitation regardless of network proximity. This makes it particularly concerning for security professionals who depend on consistent monitoring tools for their network security operations.
The mitigation strategies for this vulnerability involve immediate upgrading to Ethereal version 0.9.3 or later, which contains the necessary code fixes to properly handle malformed DNS packets and prevent infinite loop conditions. Organizations should also implement network segmentation and access controls to limit exposure to potentially malicious traffic, while monitoring for unusual CPU consumption patterns that might indicate exploitation attempts. Additionally, deploying intrusion detection systems with signature-based detection capabilities can help identify and block malicious DNS packets before they reach the vulnerable application. This vulnerability aligns with CWE-835, which addresses infinite loops in software, and represents a classic example of how protocol parsing flaws can lead to denial of service conditions. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique involving network disruption and T1595.001 for reconnaissance activities that precede exploitation attempts. The remediation process should include thorough testing of updated versions in controlled environments to ensure compatibility with existing network monitoring workflows while maintaining the security posture against this specific denial of service vector.