CVE-2005-2335 in Fetchmail
Summary
by MITRE
Buffer overflow in the POP3 client in Fetchmail before 6.2.5.2 allows remote POP3 servers to cause a denial of service and possibly execute arbitrary code via long UIDL responses. NOTE: a typo in an advisory accidentally used the wrong CVE identifier for the Fetchmail issue. This is the correct identifier.
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Analysis
by VulDB Data Team • 06/07/2019
The vulnerability described in CVE-2005-2335 represents a critical buffer overflow flaw within the POP3 client implementation of Fetchmail software versions prior to 6.2.5.2. This issue resides in the handling of UIDL (Unique ID List) responses from remote POP3 servers, which are essential for email synchronization and message identification. The flaw stems from inadequate input validation and buffer management within the client-side parsing logic, creating a scenario where malicious or compromised POP3 servers can exploit this weakness to disrupt normal email operations.
The technical nature of this vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and CWE-787, concerning out-of-bounds writes. When a POP3 server sends an excessively long UIDL response, the Fetchmail client fails to properly validate the response length before copying data into fixed-size buffers. This condition allows attackers to overwrite adjacent memory locations, potentially leading to arbitrary code execution or system crashes. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1203, where adversaries manipulate application behavior through input manipulation to achieve unauthorized system control.
The operational impact of this vulnerability extends beyond simple denial of service, as it creates opportunities for remote code execution on systems running vulnerable Fetchmail versions. Organizations relying on Fetchmail for email retrieval become susceptible to attacks where malicious POP3 servers can inject malicious payloads into the client process, potentially compromising entire email infrastructure. The vulnerability affects systems where Fetchmail acts as a mail retriever, particularly those configured to automatically fetch emails from multiple sources, making it a significant concern for enterprise email management systems.
Mitigation strategies for CVE-2005-2335 primarily involve upgrading to Fetchmail version 6.2.5.2 or later, which includes proper input validation and buffer size checks for UIDL responses. System administrators should also implement network-level filtering to restrict access to known legitimate POP3 servers and deploy intrusion detection systems to monitor for suspicious UIDL response patterns. Additional protective measures include configuring Fetchmail with stricter security parameters, such as limiting the maximum response size that can be processed, and implementing network segmentation to isolate email retrieval systems from potentially compromised network segments. The vulnerability serves as a reminder of the critical importance of proper input validation in network protocols and the potential for remote exploitation through seemingly benign email server interactions.