CVE-2008-5839 in Foxmail
Summary
by MITRE
Buffer overflow in Foxmail 6.5 allows remote attackers to execute arbitrary code via a long mailto URI in the HREF attribute of an A element.
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Analysis
by VulDB Data Team • 05/24/2025
The vulnerability identified as CVE-2008-5839 represents a critical buffer overflow flaw within Foxmail version 6.5 that enables remote code execution through maliciously crafted mailto URIs. This security defect manifests when the email client processes a specially constructed hyperlink containing an excessively long mailto URI within the href attribute of an anchor element. The flaw stems from inadequate input validation and bounds checking mechanisms within the Foxmail application's URI parsing functionality, creating an exploitable condition that can be leveraged by remote attackers to gain unauthorized control over affected systems.
The technical implementation of this vulnerability involves the manipulation of the HREF attribute within HTML anchor tags to contain an overly long mailto URI string that exceeds the allocated buffer space within Foxmail's processing routines. When the application attempts to parse and handle this malformed URI, it fails to properly validate the input length, leading to a classic buffer overflow condition where adjacent memory regions become overwritten with attacker-controlled data. This memory corruption typically results in the execution of arbitrary code at the privilege level of the running Foxmail process, which often operates with elevated permissions depending on the system configuration. The vulnerability specifically affects the application's handling of web-based email links that users might encounter while browsing the internet or receiving malicious emails containing such crafted links.
From an operational impact perspective, this vulnerability presents a significant risk to users who may inadvertently click on malicious links within email messages or web content while using Foxmail 6.5. The attack vector requires social engineering to convince users to interact with the malicious content, but once triggered, the exploit can lead to complete system compromise including privilege escalation, data exfiltration, and persistent backdoor installation. The vulnerability is particularly dangerous because it can be exploited through standard web browsing activities, making it a common target for phishing campaigns and drive-by download attacks. The attack surface extends beyond individual user systems to potentially affect entire organizational email infrastructures where Foxmail is widely deployed.
Mitigation strategies for this vulnerability should include immediate deployment of vendor-provided security patches and updates to Foxmail versions that address the buffer overflow condition. System administrators should implement network-based security controls such as email filtering and web content filtering to block suspicious mailto URI patterns and prevent users from accessing potentially malicious content. Additionally, user education and awareness programs should emphasize the importance of avoiding suspicious email links and web content. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and maps to ATT&CK technique T1203, which covers exploitation of remote services through malformed input. Organizations should also consider implementing application whitelisting policies to restrict execution of untrusted code and maintain regular vulnerability assessments to identify similar flaws in other email client applications. Given the age of this vulnerability and the lack of vendor support for Foxmail 6.5, upgrading to modern email clients with robust security features represents the most effective long-term solution to prevent exploitation of this and similar buffer overflow vulnerabilities.