CVE-2006-0449 in SPA-PRO Mail @Solomon
Summary
by MITRE
Early termination vulnerability in the IMAP service in E-Post Mail 4.05 and SPA-PRO Mail 4.05 allows remote attackers to cause a denial of service (infinite loop) by sending an APPEND command and disconnecting before the expected amount of data is sent.
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Analysis
by VulDB Data Team • 06/08/2017
The vulnerability described in CVE-2006-0449 represents a classic early termination flaw within the IMAP service implementation of E-Post Mail 4.05 and SPA-PRO Mail 4.05 email servers. This issue manifests as a denial of service condition that occurs when a remote attacker exploits a specific communication pattern during the APPEND command execution. The flaw stems from the server's inadequate handling of incomplete data transfers, creating a scenario where the service enters an infinite loop when the client disconnects prematurely during data transmission. This type of vulnerability falls under the broader category of improper input handling and demonstrates a critical weakness in the protocol state management of the affected mail servers.
The technical implementation of this vulnerability exploits the fundamental communication flow within IMAP services where clients can append messages to mailboxes through the APPEND command. When a client initiates an APPEND operation, the server typically expects to receive a complete message payload before processing it. However, in the vulnerable versions of these mail servers, the system fails to properly validate or handle the case where a client sends an initial APPEND command and then disconnects before transmitting the full expected data. This premature disconnection causes the server to enter a loop where it continuously waits for data that will never arrive, effectively consuming system resources and rendering the service unavailable to legitimate users. The vulnerability operates at the application layer and specifically targets the IMAP protocol implementation, making it particularly dangerous in environments where email services are critical for business operations.
The operational impact of this vulnerability extends beyond simple service disruption to create significant reliability issues for organizations relying on these email systems. The infinite loop condition consumes CPU cycles and memory resources, potentially leading to system crashes or severe performance degradation that affects all users of the affected mail server. Network administrators may find their systems becoming unresponsive to legitimate email operations, as the server becomes trapped in processing the malformed APPEND command sequence. This type of denial of service attack is particularly insidious because it requires minimal resources from the attacker while potentially causing maximum disruption to service availability. The vulnerability also demonstrates poor error handling practices that could indicate broader security weaknesses in the application's architecture and input validation mechanisms.
Mitigation strategies for this vulnerability should focus on both immediate patching and architectural improvements to prevent similar issues. Organizations should prioritize updating to versions of E-Post Mail and SPA-PRO Mail that address this specific flaw, as the vulnerability is well-documented and has been resolved in subsequent releases. Network-level protections such as implementing rate limiting and connection monitoring can help detect and prevent exploitation attempts. The vulnerability aligns with CWE-400, which covers improper handling of input that can lead to resource exhaustion, and relates to ATT&CK technique T1499.004 for network denial of service attacks. Additionally, implementing proper timeout mechanisms and robust input validation in IMAP protocol implementations would prevent similar early termination vulnerabilities from occurring in the future, emphasizing the importance of defensive programming practices and comprehensive testing of protocol state transitions in network services.