CVE-2005-2070 in Mail Filter
Summary
by MITRE
The ClamAV Mail fILTER (clamav-milter) 0.84 through 0.85d, when used in Sendmail using long timeouts, allows remote attackers to cause a denial of service by keeping an open connection, which prevents ClamAV from reloading.
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Analysis
by VulDB Data Team • 07/05/2021
The vulnerability identified as CVE-2005-2070 affects the ClamAV Mail fILTER component known as clamav-milter version 0.84 through 0.85d when integrated with Sendmail mail server. This issue represents a classic denial of service vulnerability that exploits the interaction between mail filtering mechanisms and connection handling timeouts. The flaw specifically manifests when the system operates with long timeout configurations, creating a window where malicious actors can manipulate connection states to disrupt normal service operations.
The technical implementation of this vulnerability stems from how clamav-milter manages persistent connections within the Sendmail framework. When connections remain open for extended periods due to long timeout settings, the malicious actor can maintain these connections indefinitely without sending actual mail content. This behavior prevents the ClamAV daemon from performing its regular reload operations, which are essential for updating virus definitions and maintaining system security. The underlying mechanism operates through the milter protocol interface, where the filter maintains connection state information that should normally be cleared upon connection termination.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader security implications. Organizations relying on ClamAV for email content filtering face potential exposure to persistent denial of service attacks that can remain undetected for extended periods. The vulnerability creates a scenario where legitimate mail processing is blocked while the malicious connection remains active, potentially allowing attackers to maintain their foothold without immediate detection. This type of attack pattern aligns with the attacker technique category of resource exhaustion as outlined in the MITRE ATT&CK framework, specifically targeting system availability through connection management manipulation.
From a security standards perspective, this vulnerability maps to CWE-400 which describes unchecked resource exhaustion, and CWE-119 which addresses memory corruption through improper handling of resources. The issue demonstrates poor resource management practices where connection states are not properly timed out or cleaned up, creating a persistent resource leak that eventually leads to system instability. The vulnerability also reflects weak input validation and connection handling mechanisms that should be addressed through proper timeout configuration and connection state management protocols.
Mitigation strategies for CVE-2005-2070 require immediate attention to connection timeout configurations within the Sendmail and ClamAV integration. System administrators should implement shorter connection timeouts to prevent indefinite connection maintenance by unauthorized parties. The recommended approach involves configuring appropriate milter timeout values that balance legitimate processing requirements with security considerations. Additionally, implementing network-level monitoring to detect unusual connection patterns and establishing regular service restart procedures can provide additional defense layers. The solution approach aligns with the principle of least privilege and defense in depth as specified in cybersecurity frameworks, ensuring that connection management policies are properly enforced throughout the mail processing pipeline. Organizations should also consider upgrading to newer versions of ClamAV where these connection handling issues have been addressed through improved timeout mechanisms and more robust state management protocols.