CVE-2001-1009 in Fetchmail
Summary
by MITRE
Fetchmail (aka fetchmail-ssl) before 5.8.17 allows a remote malicious (1) IMAP server or (2) POP/POP3 server to overwrite arbitrary memory and possibly gain privileges via a negative index number as part of a response to a LIST request.
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Analysis
by VulDB Data Team • 01/19/2025
The vulnerability identified as CVE-2001-1009 affects fetchmail-ssl versions prior to 5.8.17, representing a critical memory corruption issue that could potentially lead to privilege escalation. This vulnerability specifically manifests when fetchmail processes responses from IMAP or POP3 servers, creating a scenario where malicious servers can manipulate the application's memory handling mechanisms through crafted negative index values during LIST command responses.
The technical flaw resides in fetchmail's improper validation of index numbers received from mail servers during the LIST command execution process. When fetchmail encounters a negative index number in a server response, it fails to properly bounds-check this value before using it to access memory locations. This lack of input validation creates a classic buffer overflow condition where malicious servers can cause the application to write data to arbitrary memory addresses, potentially overwriting critical program structures or executable code.
From an operational impact perspective, this vulnerability presents a significant threat to email security infrastructure since fetchmail is commonly used for retrieving emails from remote servers and forwarding them to local mail servers. An attacker controlling a malicious IMAP or POP3 server could exploit this weakness to execute arbitrary code with the privileges of the fetchmail process, which typically runs with elevated permissions to access user mailboxes and system resources. The vulnerability's remote nature means that attackers do not need physical access to the target system, making it particularly dangerous for organizations relying on fetchmail for email retrieval.
The vulnerability aligns with CWE-129, which addresses improper validation of array indices, and represents a memory safety issue that could be categorized under ATT&CK technique T1059 for command and scripting interpreter usage. The attack vector involves a man-in-the-middle position where the malicious server intercepts communication between fetchmail and legitimate email servers, or alternatively, a compromised email server that has been modified to send malicious responses. This vulnerability could be exploited in conjunction with other attack vectors to establish persistent access or escalate privileges within the target environment.
Organizations should immediately upgrade to fetchmail version 5.8.17 or later, which implements proper bounds checking for index values received from mail servers. System administrators should also consider implementing network segmentation and monitoring for unusual LIST command responses, as well as applying network-level controls to restrict fetchmail's access to trusted mail servers only. Additionally, regular security auditing of email infrastructure components and maintaining up-to-date vulnerability assessments are crucial for preventing exploitation of similar memory corruption vulnerabilities in other email client applications.