CVE-2002-1365 in Fetchmail
Summary
by MITRE
Heap-based buffer overflow in Fetchmail 6.1.3 and earlier does not account for the "@" character when determining buffer lengths for local addresses, which allows remote attackers to execute arbitrary code via a header with a large number of local addresses.
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Analysis
by VulDB Data Team • 09/06/2025
The vulnerability identified as CVE-2002-1365 represents a critical heap-based buffer overflow in Fetchmail versions 6.1.3 and earlier, specifically affecting the handling of email headers containing local addresses. This flaw stems from an inadequate buffer length calculation mechanism that fails to properly account for the "@" character when processing email addresses within message headers. The vulnerability exists within the mail retrieval and processing functionality of Fetchmail, which is widely used for retrieving emails from remote servers and delivering them locally. The issue manifests when the software processes email headers containing a large number of local addresses, creating conditions where memory allocation becomes insufficient to handle the actual data being processed.
The technical exploitation of this vulnerability occurs through manipulation of email headers that contain an excessive number of local addresses, particularly those containing the "" character. When Fetchmail processes such headers, it calculates buffer sizes based on assumptions that do not properly consider the presence of the "" character in local address components. This miscalculation results in insufficient memory allocation, leading to heap corruption when the software attempts to write data beyond the allocated buffer boundaries. The heap overflow condition creates opportunities for attackers to execute arbitrary code with the privileges of the Fetchmail process, potentially allowing full system compromise. This vulnerability directly maps to CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation leading to memory corruption.
The operational impact of CVE-2002-1365 extends beyond simple code execution, as it can enable attackers to gain unauthorized access to systems running vulnerable Fetchmail versions. Since Fetchmail is commonly used in email server configurations and is often run with elevated privileges, successful exploitation could lead to complete system compromise. The vulnerability is particularly dangerous in environments where email processing is automated, as attackers could craft malicious emails to trigger the overflow without requiring user interaction. This makes the vulnerability suitable for automated exploitation and increases its potential impact. The attack vector leverages the standard email protocol processing mechanisms, making it difficult to detect through conventional network monitoring. The vulnerability also aligns with ATT&CK technique T1059.007, which covers command and scripting interpreter usage through email-based attacks.
Mitigation strategies for CVE-2002-1365 require immediate patching of Fetchmail installations to versions 6.1.4 and later, which contain the necessary fixes to properly account for the "" character in buffer length calculations. System administrators should also implement email filtering mechanisms that can detect and block malformed headers containing excessive local addresses. Network segmentation and access controls should be enforced to limit exposure of vulnerable systems to untrusted email sources. Additionally, regular security audits should verify that all email processing components are updated to their latest secure versions. The fix implemented in subsequent versions addresses the core buffer calculation logic by properly accounting for all characters in local address components, including the "" symbol, thereby preventing the heap overflow condition from occurring. Organizations should also consider implementing email header length validation as part of their security monitoring procedures to detect potential exploitation attempts.