CVE-2005-4592 in Email Filter
Summary
by MITRE
Heap-based buffer overflow in bogofilter and bogolexer 0.96.2 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via words that are longer than the input buffer used by flex.
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Analysis
by VulDB Data Team • 06/18/2019
The vulnerability described in CVE-2005-4592 represents a critical heap-based buffer overflow affecting the bogofilter and bogolexer software versions 0.96.2. This flaw resides in the lexical analysis component of these email filtering tools, specifically within the flex library processing mechanism. The vulnerability manifests when the software encounters input text containing words that exceed the allocated buffer size, creating conditions where memory corruption can occur. The affected applications are designed to filter spam emails by analyzing text content, making them attractive targets for attackers seeking to disrupt email services or gain unauthorized system access.
The technical root cause of this vulnerability stems from improper input validation within the flex-generated lexical analyzer. When flex processes input text, it allocates fixed-size buffers to store tokenized words, but fails to adequately check the length of incoming words before copying them into these buffers. This classic buffer overflow condition occurs because the software assumes all input words will fit within predetermined memory boundaries without performing length validation. The heap-based nature of the overflow means that the corrupted memory exists in the heap allocation area rather than on the stack, which can lead to more complex exploitation scenarios and potentially allow for arbitrary code execution. This vulnerability aligns with CWE-121, heap-based buffer overflow, and represents a common weakness in software implementations that do not properly validate input lengths against allocated buffer sizes.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable remote code execution, making it particularly dangerous for email servers and spam filtering systems. An attacker could craft specially formatted email messages containing excessively long words or sequences that would trigger the buffer overflow when processed by the bogofilter or bogolexer applications. The crash conditions would result in service disruption, effectively creating a denial of service scenario that could be exploited repeatedly to maintain persistent disruption of email services. In more sophisticated attack scenarios, the heap corruption could be manipulated to redirect program execution flow, potentially allowing attackers to execute malicious code with the privileges of the affected service. This vulnerability directly maps to attack techniques described in the ATT&CK framework under T1499 for network denial of service and T1059 for command and control communications through compromised email systems.
Mitigation strategies for this vulnerability should focus on immediate software updates to patched versions of bogofilter and bogolexer, as well as implementing additional input validation measures within email processing pipelines. Organizations should consider deploying intrusion detection systems that can identify and block malformed email content that might trigger this vulnerability. Network segmentation and access controls should be implemented to limit exposure of vulnerable systems, while regular security audits should verify that all email filtering components are running patched versions. The vulnerability highlights the importance of input validation in lexical analysis components and underscores the need for thorough testing of boundary conditions in text processing applications. System administrators should also implement monitoring solutions that can detect unusual crash patterns or service disruptions that might indicate exploitation attempts, while maintaining up-to-date threat intelligence to identify similar vulnerabilities in other software components.