CVE-2009-0068 in Xdg-utils
Summary
by MITRE
Interaction error in xdg-open allows remote attackers to execute arbitrary code by sending a file with a dangerous MIME type but using a safe type that Firefox sends to xdg-open, which causes xdg-open to process the dangerous file type through automatic type detection, as demonstrated by overwriting the .desktop file.
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Analysis
by VulDB Data Team • 08/23/2019
The vulnerability identified as CVE-2009-0068 represents a critical interaction error within the xdg-open utility that forms part of the freedesktop.org desktop environment ecosystem. This flaw exists in the way xdg-open handles file type detection and execution, creating a pathway for remote attackers to bypass security controls through carefully crafted file MIME type manipulation. The vulnerability specifically affects systems where xdg-open is used to open files based on their MIME type, commonly encountered in Linux desktop environments and applications that rely on the freedesktop.org standards for file handling. The flaw stems from the utility's automatic MIME type detection mechanism that can be deceived by attackers who craft files with malicious content but disguise them with seemingly safe MIME types that Firefox and other browsers typically send to xdg-open for processing.
The technical implementation of this vulnerability involves a sophisticated manipulation of MIME type handling within the desktop environment's file association system. When a user clicks on a file link in a web browser, Firefox determines the appropriate MIME type and passes it to xdg-open for processing. However, the vulnerability allows attackers to exploit the automatic type detection logic by creating files with dangerous content but assigning them MIME types that xdg-open considers safe or benign. This creates a scenario where xdg-open processes the file through its automatic detection mechanism, ultimately executing the malicious content through the association with a desktop file handler. The demonstration of this vulnerability specifically shows how attackers can overwrite .desktop files, which are typically used for creating desktop shortcuts and application launchers, with malicious content that gets executed when the desktop environment processes these files.
The operational impact of CVE-2009-0068 extends beyond simple code execution to encompass potential system compromise and privilege escalation scenarios within desktop environments. This vulnerability directly affects the security model of desktop environments that rely on xdg-open for file handling, potentially allowing remote attackers to execute arbitrary commands with the privileges of the user who opens the malicious file. The attack vector is particularly concerning because it leverages the trust relationship between web browsers and desktop file handling utilities, making it difficult for users to detect malicious activity. The vulnerability operates at the intersection of web browsing and local file execution, creating a unique attack surface that combines elements of web-based exploitation with local system compromise. According to CWE classification, this vulnerability maps to CWE-170, which deals with improper handling of potentially dangerous characters or strings, and more specifically to CWE-22, representing improper limitation of a pathname to a restricted directory, as the attack involves manipulating file paths through MIME type deception.
Mitigation strategies for CVE-2009-0068 require a multi-layered approach that addresses both the immediate vulnerability and broader desktop security practices. System administrators should ensure that xdg-open and related desktop environment utilities are updated to versions that properly validate MIME types and prevent automatic type detection from being bypassed through malicious file crafting. The implementation of strict MIME type validation controls within desktop environments is essential, requiring that applications verify file types through multiple independent methods rather than relying solely on automatic detection mechanisms. Additionally, users should be educated about the risks of opening files from untrusted sources, particularly those linked through web browsers, and the importance of verifying file content before opening. Security controls should include implementing sandboxing mechanisms for file handling operations and restricting the execution of .desktop files from untrusted sources. From an ATT&CK framework perspective, this vulnerability relates to techniques involving privilege escalation through application misconfiguration and execution of malicious code through web-based delivery mechanisms, specifically mapping to techniques such as T1059 for command and scripting interpreter and T1068 for exploit for privilege escalation. Organizations should also consider implementing network-based controls that can detect and block suspicious MIME type patterns that might indicate attempts to exploit this vulnerability, as well as maintaining regular patching schedules for desktop environment components to prevent exploitation of known vulnerabilities.