CVE-2007-4242 in Security Gateway
Summary
by MITRE
The pop3 Proxy in Astaro Security Gateway (ASG) 7 does not perform virus scanning of attachments that exceed the maximum attachment size, and passes these attachments, which allows remote attackers to bypass this scanning via a large attachment.
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Analysis
by VulDB Data Team • 10/28/2017
The vulnerability described in CVE-2007-4242 represents a critical security flaw in the Astaro Security Gateway version 7 mail proxy functionality. This issue specifically affects the pop3 proxy component which is responsible for filtering and scanning email attachments before they are delivered to end users. The vulnerability stems from an improper implementation of attachment size validation that creates a bypass mechanism for malicious content. When email attachments exceed the configured maximum attachment size limit, the system fails to perform virus scanning on these oversized files and simply forwards them through the proxy without inspection. This behavior creates a significant security gap that directly contradicts the intended security posture of the mail filtering system.
The technical flaw manifests in the application's failure to maintain consistent security controls across all attachment sizes. According to CWE-200, this vulnerability represents an information exposure issue where the system provides different security treatment based on attachment size parameters. The implementation error occurs within the attachment processing pipeline of the pop3 proxy where size-based conditional logic incorrectly excludes virus scanning for oversized attachments. This design flaw creates a scenario where attackers can exploit the size limitation to deliver malicious payloads that would normally be detected and blocked by the antivirus scanning system. The vulnerability specifically impacts the integrity of the email security filtering mechanism and represents a failure in the principle of least privilege and defense in depth.
From an operational perspective, this vulnerability allows remote attackers to bypass critical security controls by simply crafting attachments that exceed the maximum size threshold. The attack vector is straightforward and requires minimal technical expertise to exploit, making it particularly dangerous in enterprise environments where email security is paramount. The bypass mechanism enables the delivery of malware, phishing attachments, or other malicious content that could compromise user systems and network infrastructure. This vulnerability undermines the trust model of the security gateway and creates a persistent threat vector that could be exploited for data exfiltration, system compromise, or lateral movement within compromised networks. The impact extends beyond immediate security breaches to include potential regulatory compliance violations and reputational damage for organizations relying on the affected security gateway.
The recommended mitigation strategies for this vulnerability include implementing proper size validation that maintains consistent security scanning regardless of attachment dimensions. Organizations should configure the security gateway to enforce virus scanning on all attachments, regardless of size, or establish strict size limits that prevent the bypass mechanism. According to ATT&CK framework technique T1190, this vulnerability relates to exploitation of remote services and could be leveraged for initial access. Security administrators should also implement network monitoring to detect unusual attachment size patterns that may indicate exploitation attempts. The fix requires either patching the software to correct the conditional logic in the attachment processing routine or reconfiguring the security gateway to maintain consistent scanning behavior across all attachment sizes. Additionally, organizations should conduct comprehensive security assessments to identify similar vulnerabilities in other components of their email infrastructure and implement proper input validation controls to prevent similar issues in the future.