CVE-2017-11421 in gnome-exe-thumbnailer
Summary
by MITRE
gnome-exe-thumbnailer before 0.9.5 is prone to a VBScript Injection when generating thumbnails for MSI files, aka the "Bad Taste" issue. There is a local attack if the victim uses the GNOME Files file manager, and navigates to a directory containing a .msi file with VBScript code in its filename.
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Analysis
by VulDB Data Team • 12/13/2022
The vulnerability identified as CVE-2017-11421 represents a critical security flaw in the gnome-exe-thumbnailer utility version 0.9.4 and earlier, which falls under the category of command injection vulnerabilities. This issue specifically affects the GNOME Files file manager's thumbnail generation process when handling Microsoft Installer (.msi) files. The vulnerability stems from improper input validation and sanitization during the thumbnail creation phase, where the system fails to adequately escape or filter special characters in filenames that contain VBScript code. When a user navigates to a directory containing an .msi file with malicious VBScript code embedded in its filename, the thumbnail generation process becomes susceptible to arbitrary code execution.
The technical implementation of this vulnerability occurs within the thumbnail generation pipeline of the gnome-exe-thumbnailer component, which is designed to create visual representations of executable files for improved file browsing experience. The flaw manifests when the utility processes filenames containing special characters that are interpreted by the underlying scripting engine, particularly VBScript, which is commonly used in Windows environments. This process typically involves calling external commands or scripts to generate the thumbnail, and the vulnerability arises from insufficient sanitization of user-supplied filenames that may contain script injection payloads. The vulnerability can be categorized under CWE-74 as "Improper Neutralization of Special Elements in Output Used by a Downstream Component" and specifically relates to CWE-94 as "Improper Control of Generation of Code ('Code Injection')".
The operational impact of CVE-2017-11421 is significant, as it enables local privilege escalation through a carefully crafted filename that can execute malicious VBScript code when the victim's GNOME Files application attempts to generate thumbnails. Attackers can exploit this vulnerability by placing specially crafted .msi files in directories that the victim frequently accesses, particularly those containing sensitive data or shared network drives. The attack vector requires the victim to have GNOME Files open and navigate to the directory containing the malicious file, making it a user-initiated attack that relies on social engineering or insider threat scenarios. This vulnerability aligns with ATT&CK technique T1059.005 as "Command and Scripting Interpreter: Visual Basic" and represents a classic example of how file manager utilities can become attack vectors when they fail to properly validate user input.
Mitigation strategies for CVE-2017-11421 focus primarily on updating to gnome-exe-thumbnailer version 0.9.5 or later, which includes proper input sanitization and filename validation mechanisms. System administrators should also consider implementing additional security measures such as disabling thumbnail previews for potentially dangerous file types, particularly .msi files, through GNOME configuration settings. The vulnerability demonstrates the importance of input validation in desktop environments where file managers automatically process and generate previews for various file types. Organizations should also implement monitoring solutions to detect unusual thumbnail generation activities and consider network segmentation to limit the potential impact of successful exploitation. Security awareness training for users can help prevent accidental navigation to directories containing maliciously crafted files, while application whitelisting policies can further reduce the risk of arbitrary code execution through file manager utilities.