CVE-2000-1022 in PIX
Summary
by MITRE
The mailguard feature in Cisco Secure PIX Firewall 5.2(2) and earlier does not properly restrict access to SMTP commands, which allows remote attackers to execute restricted commands by sending a DATA command before sending the restricted commands.
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Analysis
by VulDB Data Team • 10/11/2025
The vulnerability identified as CVE-2000-1022 affects Cisco Secure PIX Firewall versions 5.2(2) and earlier, specifically targeting the mailguard feature implementation. This security flaw represents a critical access control weakness that undermines the firewall's ability to properly enforce email command restrictions. The vulnerability stems from improper validation of SMTP command sequences within the mailguard functionality, creating a pathway for malicious actors to bypass intended security controls. The issue manifests when attackers exploit the sequence in which SMTP commands are processed, allowing them to execute restricted operations that should normally be prohibited.
The technical implementation flaw resides in the mailguard component's handling of SMTP protocol interactions, particularly during the data transfer phase of email communication. When a DATA command is sent prior to restricted SMTP commands, the firewall fails to properly validate the command sequence and authorization status of the requesting entity. This improper access control mechanism creates a window of opportunity where unauthorized operations can be executed without proper authentication or authorization checks. The vulnerability operates at the application layer of the network stack, specifically affecting email filtering and content inspection capabilities within the firewall's security framework.
Operationally, this vulnerability enables remote attackers to execute arbitrary SMTP commands on the affected firewall system, potentially leading to complete compromise of the email filtering functionality. Attackers can leverage this weakness to bypass email content restrictions, access restricted email services, or even gain unauthorized access to internal network resources through the compromised mailguard functionality. The impact extends beyond simple command execution as it can allow for data exfiltration, service disruption, and potential lateral movement within the network environment. This vulnerability particularly affects organizations relying on PIX firewalls for email security, as it undermines the core protection mechanisms designed to prevent unauthorized email access and content inspection.
The security implications of this vulnerability align with CWE-284 Access Control Issues, specifically addressing improper access control mechanisms in network security appliances. From an ATT&CK framework perspective, this vulnerability maps to T1190 Exploit Public-Facing Application and T1071.004 Application Layer Protocol: Email Protocols, demonstrating how weaknesses in application-level security can be exploited to gain unauthorized access to network services. Organizations should implement immediate mitigations including upgrading to patched versions of the Cisco PIX Firewall software, disabling unnecessary email filtering features, and implementing additional network segmentation controls. The vulnerability underscores the importance of proper input validation and command sequence verification in network security appliances, highlighting the need for comprehensive security testing of protocol implementations within firewall systems.