CVE-2002-0603 in Lite+ Firewall
Summary
by MITRE
Snapgear Lite+ firewall 1.5.3 allows remote attackers to cause a denial of service (IPSEC crash) via a zero length packet to UDP port 500.
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Analysis
by VulDB Data Team • 04/12/2019
The vulnerability identified as CVE-2002-0603 affects Snapgear Lite+ firewall version 1.5.3, representing a critical denial of service flaw that can be exploited remotely by attackers. This issue specifically targets the Internet Protocol Security (IPSEC) implementation within the firewall software, creating a condition where legitimate network services can be disrupted through carefully crafted network traffic. The vulnerability manifests when the system receives a zero length packet transmitted to UDP port 500, which is the standard port used for Internet Security Association and Key Management Protocol (ISAKMP) communications in IPSEC implementations.
The technical root cause of this vulnerability lies in the insufficient input validation mechanisms within the Snapgear firewall's IPSEC processing module. When the system encounters a zero length packet on UDP port 500, it fails to properly handle this malformed data structure, leading to a crash of the IPSEC service component. This behavior represents a classic buffer over-read or improper state handling vulnerability that can be categorized under CWE-129, which deals with insufficient validation of length of inputs to buffers. The flaw demonstrates poor error handling practices where the software does not adequately validate packet contents before processing them, particularly in the context of security protocol implementations that require strict adherence to protocol specifications.
The operational impact of this vulnerability extends beyond simple service disruption, as it can potentially compromise the entire network security posture of systems relying on the affected firewall. When the IPSEC service crashes, it can result in complete loss of IPSEC tunnel functionality, which may affect encrypted communications, remote access capabilities, and overall network security infrastructure. This vulnerability is particularly dangerous because it can be exploited without requiring authentication credentials, making it an attractive target for malicious actors seeking to disrupt network operations. The attack vector is straightforward, requiring only the transmission of a specially crafted zero length packet, which can be executed from any network location capable of reaching the target firewall's UDP port 500.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1499.004, which involves network disruption through denial of service attacks. The impact on network availability can be severe, especially in environments where IPSEC is critical for secure communications, such as corporate networks, government systems, or any infrastructure requiring encrypted data transmission. Organizations may experience cascading effects where the IPSEC service crash leads to broader network instability, as other dependent services may fail to function properly when IPSEC tunnels are disrupted. The vulnerability also demonstrates the importance of proper network segmentation and monitoring, as such attacks can go unnoticed until service degradation becomes apparent.
The recommended mitigations for this vulnerability include immediate application of vendor patches or updates to the Snapgear firewall software, as well as network-level protections such as firewall rules that block or limit traffic to UDP port 500 from untrusted sources. Network administrators should also implement monitoring solutions that can detect anomalous packet patterns and zero length packet deliveries to UDP ports. Additionally, organizations should consider implementing intrusion detection systems that can identify potential exploitation attempts of this specific vulnerability. The fix typically involves implementing proper input validation mechanisms that can gracefully handle malformed packets, ensuring that zero length packets are either rejected or properly processed without causing service crashes. This vulnerability serves as a reminder of the critical importance of robust input validation in security-sensitive applications and the necessity of regular security updates to address known vulnerabilities in network infrastructure components.