CVE-2010-3354 in dropbox
Summary
by MITRE
dropboxd in Dropbox 0.7.110 places a zero-length directory name in the LD_LIBRARY_PATH, which allows local users to gain privileges via a Trojan horse shared library in the current working directory.
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Analysis
by VulDB Data Team • 02/07/2019
The vulnerability described in CVE-2010-3354 represents a classic privilege escalation flaw that exploits improper environment variable handling within the Dropbox client software. This issue affects Dropbox version 0.7.110 and demonstrates how seemingly minor configuration errors can create significant security risks. The flaw occurs in the dropboxd daemon process which is responsible for managing Dropbox synchronization operations in the background. When this daemon initializes, it inadvertently includes a zero-length directory name within the LD_LIBRARY_PATH environment variable, creating an exploitable condition that local attackers can leverage.
The technical mechanism behind this vulnerability involves the manipulation of the dynamic linker's library search path through the LD_LIBRARY_PATH environment variable. When a zero-length directory is included in this path, it effectively translates to the current working directory, which is represented as an empty string in the path resolution process. This behavior violates the principle of least privilege and creates a scenario where any shared library named identically to a system library present in the current working directory will be loaded before the legitimate system libraries. The vulnerability is categorized under CWE-427 Uncontrolled Search Path Element, which specifically addresses the risk of attackers placing malicious code in directories that are searched by applications.
From an operational perspective, this vulnerability allows local users to execute arbitrary code with elevated privileges, potentially leading to complete system compromise. Attackers can create a Trojan horse shared library in their current working directory with the same name as a legitimate system library that dropboxd would normally load. When the dropboxd daemon runs and processes this modified library path, it loads the malicious version instead of the legitimate system library, enabling privilege escalation. The attack requires local system access but does not require network connectivity or user interaction, making it particularly dangerous in multi-user environments where users might not be properly isolated.
The impact of this vulnerability extends beyond simple privilege escalation, as it can be leveraged to establish persistent access or to perform more sophisticated attacks. The issue demonstrates the importance of proper environment variable sanitization and the dangers of including user-controllable elements in system paths. According to ATT&CK framework, this vulnerability maps to T1068 Privilege Escalation through the exploitation of environment variable manipulation techniques. The vulnerability also aligns with T1548.001 Account Manipulation and T1059 Command and Scripting Interpreter, as attackers can use the elevated privileges to modify system accounts or execute commands through the compromised dropboxd process.
Mitigation strategies for this vulnerability involve several layers of defensive measures. The most direct fix is to update to a patched version of Dropbox that properly handles the LD_LIBRARY_PATH environment variable by removing or sanitizing empty directory entries. System administrators should also implement proper file system permissions and monitoring to detect unauthorized library modifications. The principle of least privilege should be enforced by ensuring that daemon processes do not run with unnecessary elevated permissions. Additionally, security tools can be configured to monitor for suspicious library loading patterns and environment variable modifications. Organizations should also consider implementing application whitelisting policies that restrict which libraries can be loaded by critical system processes, thereby preventing the loading of unauthorized shared objects even if the environment variable path is compromised.