CVE-2007-4841 in Firefox
Summary
by MITRE
Mozilla Firefox before 2.0.0.8, Thunderbird before 2.0.0.8, and SeaMonkey before 1.1.5 allows remote attackers to execute arbitrary commands via a (1) mailto, (2) nntp, (3) news, or (4) snews URI with invalid "%" encoding, related to improper file type handling on Windows XP with Internet Explorer 7 installed, a variant of CVE-2007-3845.
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Analysis
by VulDB Data Team • 03/16/2021
This vulnerability represents a critical remote code execution flaw affecting Mozilla Firefox, Thunderbird, and SeaMonkey email clients prior to specific version releases. The issue stems from improper handling of specially crafted URI schemes including mailto, nntp, news, and snews when they contain invalid "%" encoding sequences. The vulnerability specifically manifests on Windows XP systems running Internet Explorer 7, creating a dangerous intersection between browser and email client security implementations. Attackers can exploit this weakness by crafting malicious email messages or web content that triggers the vulnerable URI handlers, potentially leading to arbitrary code execution on target systems. The root cause lies in the applications' failure to properly validate and sanitize URI encoding before processing these specific protocol handlers, creating a pathway for malicious input to bypass normal security boundaries. This vulnerability directly relates to CWE-170, which addresses improper input handling and encoding issues that can lead to security breaches.
The technical exploitation of this vulnerability requires understanding how Windows Internet Explorer 7 interacts with these URI schemes when processed through the affected Mozilla applications. When a user encounters an email message or web page containing a malformed URI with invalid percent encoding, the vulnerable applications attempt to process these URLs through the Windows shell or browser integration components. This process can trigger unexpected behavior where the invalid encoding sequences are interpreted as commands or file paths, potentially allowing attackers to execute arbitrary code with the privileges of the affected user. The vulnerability's impact is amplified on Windows XP systems due to the specific integration points between the Mozilla applications and Windows shell components, creating multiple attack vectors that can be leveraged across different email protocols.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass potential system compromise and data exfiltration capabilities. Attackers can craft sophisticated phishing campaigns that deliver malicious URIs through email messages, web pages, or instant messaging protocols, making this vulnerability particularly dangerous in enterprise environments. The fact that this vulnerability affects multiple Mozilla products including email clients and web browsers creates a broader attack surface that security teams must consider when implementing protective measures. Organizations using these affected versions face significant risk of unauthorized access, system takeover, and potential lateral movement within their networks, especially when users interact with untrusted email content or web resources. The vulnerability also demonstrates the importance of proper URI validation and encoding handling in cross-platform applications.
Mitigation strategies for this vulnerability focus primarily on immediate software updates to the patched versions of Firefox, Thunderbird, and SeaMonkey. Security administrators should prioritize deployment of the respective security patches released by Mozilla to address the improper URI handling and encoding validation issues. Additionally, implementing network-level controls such as email filtering and web content restrictions can provide additional defense-in-depth layers. Organizations should consider disabling or restricting the processing of potentially malicious URI schemes through browser and email client configurations. The vulnerability's classification under ATT&CK technique T1203 highlights the need for monitoring and alerting on suspicious URI processing activities. Network administrators should also consider implementing sandboxing mechanisms and user privilege restrictions to limit the potential damage from successful exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to ensure all affected systems are properly patched and monitored for similar encoding-related vulnerabilities.