CVE-2005-4591 in Email Filter
Summary
by MITRE
Heap-based buffer overflow in bogofilter 0.96.2, 0.95.2, 0.94.14, 0.94.12, and other versions from 0.93.5 to 0.96.2, when using Unicode databases, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via "invalid input sequences" that lead to heap corruption when bogofilter or bogolexer converts character sets.
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Analysis
by VulDB Data Team • 06/18/2019
The vulnerability identified as CVE-2005-4591 represents a critical heap-based buffer overflow in the bogofilter email spam filtering tool affecting versions from 0.93.5 through 0.96.2. This flaw specifically manifests when the software processes Unicode database files, creating a dangerous condition where malformed input sequences can trigger memory corruption. The vulnerability operates through the character set conversion process that occurs when bogofilter or its associated bogolexer component handles Unicode data, making it particularly dangerous in email processing environments where diverse character encodings are common.
The technical mechanism behind this vulnerability involves improper bounds checking during character set conversion operations within the heap memory management system. When bogofilter encounters invalid Unicode input sequences in database files, the application fails to properly validate the length of incoming character data before copying it into fixed-size heap buffers. This fundamental flaw allows attackers to craft specially malformed input that exceeds buffer boundaries, leading to heap corruption that can result in program termination or potentially arbitrary code execution. The vulnerability is classified under CWE-121 as a heap-based buffer overflow, which is a well-documented weakness in memory management that has been exploited in numerous security incidents throughout the history of software development.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution, making it a significant threat to email security infrastructure. Email servers and filtering systems that rely on bogofilter for spam detection become vulnerable to exploitation by attackers who can craft malicious email content or database entries that trigger the buffer overflow condition. The remote attack vector means that an attacker does not need local access to the system to exploit this vulnerability, making it particularly dangerous in networked environments. When exploited successfully, the heap corruption can cause the application to crash or potentially allow an attacker to inject and execute arbitrary code with the privileges of the bogofilter process, which could lead to complete system compromise.
Mitigation strategies for this vulnerability require immediate patching of affected bogofilter installations to versions that address the character set conversion flaws. Organizations should also implement input validation measures that filter or sanitize Unicode data before it reaches the bogofilter processing pipeline. Network administrators should consider implementing additional email filtering layers and monitoring for unusual processing patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management in security-critical applications and highlights the need for thorough input validation, particularly when handling character encoding conversions. Security professionals should also consider implementing sandboxing techniques for email processing components and regularly updating all security tools to protect against known vulnerabilities. This case study exemplifies how seemingly minor implementation flaws in character encoding handling can lead to significant security risks in widely deployed software applications.