CVE-2004-0666 in popclient
Summary
by MITRE
Off-by-one error in the POP3_readmsg function in popclient 3.0b6 allows remote attackers to cause a denial of service (application crash) via an e-mail message with a certain line length, which leads to a buffer overflow.
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Analysis
by VulDB Data Team • 06/19/2018
The vulnerability described in CVE-2004-0666 represents a critical buffer overflow condition within the popclient 3.0b6 software package that specifically affects the POP3_readmsg function. This flaw manifests as an off-by-one error, a common class of programming defect that occurs when a program processes one element too many or too few in a data structure, leading to unpredictable behavior and potential system compromise. The vulnerability exists within the email client's message parsing functionality, where it fails to properly validate line length parameters during the processing of incoming email messages through the Post Office Protocol version 3.
The technical implementation of this vulnerability stems from improper boundary checking within the POP3_readmsg function, which handles the reading and processing of email messages from POP3 servers. When an attacker crafts a malicious email message containing a line of specific length that exceeds the allocated buffer space by exactly one byte, the program's memory management fails catastrophically. This off-by-one condition creates a scenario where the application attempts to write beyond the bounds of its allocated memory buffer, causing memory corruption that results in an application crash or complete denial of service. The vulnerability is particularly dangerous because it requires no authentication or special privileges from the attacker, making it a remote exploit that can be triggered simply by sending a specially crafted email message to a vulnerable system.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a fundamental flaw in how the email client handles message parsing and memory allocation. Systems running popclient 3.0b6 become susceptible to repeated denial of service attacks that can render email services unavailable to legitimate users, potentially causing significant operational downtime for organizations relying on these email clients. The vulnerability also demonstrates poor defensive programming practices and highlights the importance of proper input validation and boundary checking in network-facing applications. From an attack perspective, this flaw aligns with the ATT&CK technique of Denial of Service and represents a classic example of how seemingly minor programming errors can create substantial security risks. The vulnerability has been classified under CWE-129 as an Improper Validation of Array Index, which specifically addresses issues where array indices are not properly validated before use.
Mitigation strategies for this vulnerability require immediate patching of the affected popclient software to version 3.0b7 or later, which contains the necessary fixes for the buffer overflow condition. System administrators should also implement network-level protections such as email filtering and content inspection to prevent malicious messages from reaching vulnerable systems, though these measures provide only partial protection since the vulnerability exists within the core message processing functionality. Additionally, organizations should consider implementing intrusion detection systems that can identify patterns of exploitation attempts targeting this specific vulnerability. The fix for this issue demonstrates the importance of thorough code review and testing, particularly for functions that handle untrusted input from network sources, and serves as a reminder of the critical need for proper buffer management and input validation in security-sensitive applications. This vulnerability underscores the necessity of following secure coding practices and adhering to industry standards such as those outlined in the OWASP Top Ten and NIST guidelines for secure software development.