CVE-2003-1004 in PIX
Summary
by MITRE
Cisco PIX firewall 6.2.x through 6.2.3, when configured as a VPN Client, allows remote attackers to cause a denial of service (dropped IPSec tunnel connection) via an IKE Phase I negotiation request to the outside interface of the firewall.
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Analysis
by VulDB Data Team • 06/27/2019
The vulnerability described in CVE-2003-1004 represents a critical denial of service weakness in Cisco PIX firewalls running software versions 6.2.x through 6.2.3 when configured in VPN client mode. This flaw specifically targets the Internet Key Exchange protocol version 1 implementation within the firewall's IPSec infrastructure, creating a scenario where legitimate network traffic can be disrupted through carefully crafted malicious requests. The vulnerability manifests when an unauthorized remote attacker sends a specially constructed IKE Phase 1 negotiation request to the firewall's outside interface, which then triggers an improper handling of the malformed packet that leads to the termination of active IPSec tunnel connections.
The technical root cause of this vulnerability stems from inadequate input validation and error handling within the IKE Phase 1 processing logic of the affected Cisco PIX firewall versions. When the firewall receives an unexpected or malformed IKE negotiation request, the system fails to properly validate the incoming packet structure and authentication parameters, resulting in a cascading failure that terminates existing IPSec tunnels. This behavior aligns with CWE-20, which describes improper input validation as a fundamental weakness that can lead to various security issues including denial of service conditions. The flaw operates at the network protocol level, specifically within the IPSec framework that governs secure communications between network devices, making it particularly dangerous in environments where continuous secure connectivity is essential for business operations.
The operational impact of this vulnerability extends beyond simple service disruption, as it fundamentally compromises the reliability and availability of secure communications channels that organizations depend upon. When an attacker successfully exploits this weakness, they can cause multiple active IPSec tunnels to drop simultaneously, potentially affecting critical business applications that rely on encrypted connections for data transmission. This disruption can occur without any authentication or authorization requirements from the attacker, making it particularly concerning for network security administrators who must maintain continuous availability of their security infrastructure. The attack vector specifically targets the outside interface of the firewall, indicating that even externally accessible VPN endpoints can be exploited to cause internal service disruption, potentially affecting the entire network security posture.
Organizations utilizing affected Cisco PIX firewall versions should implement immediate mitigations to address this vulnerability, including applying the appropriate software patches released by Cisco as part of their security advisory process. Network administrators should also consider implementing additional monitoring and intrusion detection measures to identify potential exploitation attempts, as the vulnerability can be leveraged to cause significant service degradation without leaving obvious traces of compromise. The ATT&CK framework categorizes this type of vulnerability under the T1499.004 technique for network denial of service, where adversaries leverage protocol-level weaknesses to disrupt network services and communications. Additionally, organizations should review their firewall configuration practices to ensure that unnecessary external access to VPN endpoints is minimized and that proper access controls are implemented to reduce the attack surface available to potential adversaries attempting to exploit this vulnerability.