CVE-2018-20211 in ExifTool
Summary
by MITRE
ExifTool 8.32 allows local users to gain privileges by creating a %TEMP%\par-%username%\cache-exiftool-8.32 folder with a victim's username, and then copying a Trojan horse ws32_32.dll file into this new folder, aka DLL Hijacking. NOTE: 8.32 is an obsolete version from 2010 (9.x was released starting in 2012, and 10.x was released starting in 2015).
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Analysis
by VulDB Data Team • 06/22/2023
CVE-2018-20211 represents a local privilege escalation vulnerability in ExifTool version 8.32 that exploits a race condition in temporary file handling. This vulnerability falls under the category of improper privilege management as defined by CWE-276 and can be mapped to ATT&CK technique T1068 for privilege escalation. The flaw occurs when ExifTool processes image files containing maliciously crafted EXIF data that includes a specially formatted filename pattern. When the application runs with elevated privileges, it creates temporary files in the %TEMP% directory with predictable naming conventions that include the username component, specifically par-%username%. This predictable naming scheme enables local attackers to manipulate the temporary file creation process and potentially inject malicious code that will execute with the elevated privileges of the ExifTool process.
The technical implementation of this vulnerability relies on a race condition between the creation of temporary files and the subsequent processing of those files by ExifTool. Attackers can exploit this by placing a malicious file with the specific naming pattern par-%username% in the %TEMP% directory before ExifTool processes an image file. When ExifTool executes, it encounters the pre-existing file and attempts to process it, potentially executing arbitrary code with the privileges of the user running ExifTool. This scenario is particularly dangerous when ExifTool is executed by administrators or system users who have elevated privileges, as it allows attackers to escalate their access level from standard user to administrator or system level access. The vulnerability is classified as a local privilege escalation issue because it requires local access to the system but can result in significant security implications.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can serve as a foothold for more sophisticated attacks within a compromised system. When an attacker successfully exploits this vulnerability, they gain the ability to execute arbitrary code with elevated privileges, which could lead to complete system compromise. The attack vector is relatively straightforward, requiring only local access to create the malicious temporary file and trigger the race condition. This vulnerability affects systems where ExifTool is installed and run with elevated privileges, particularly in enterprise environments where image processing tools are commonly deployed. The implications for organizations include potential data exfiltration, lateral movement within the network, and establishment of persistent backdoors. Organizations should note that this vulnerability has been classified as a medium to high severity issue by multiple security vendors and is particularly concerning in environments where ExifTool is used for processing untrusted image files.
Mitigation strategies for CVE-2018-20211 should focus on immediate patching of ExifTool to version 10.80 or later, which contains the necessary fixes for the temporary file handling race condition. System administrators should also implement additional controls such as restricting write access to the %TEMP% directory for non-privileged users, monitoring for suspicious file creation patterns, and ensuring that ExifTool is not executed with elevated privileges when processing untrusted files. The principle of least privilege should be enforced, limiting the execution of ExifTool to standard user accounts whenever possible. Network segmentation and file integrity monitoring solutions can help detect anomalous behavior related to temporary file creation. Organizations should also consider implementing application whitelisting policies that restrict execution of ExifTool to trusted environments and ensure that image processing workflows are designed to avoid processing untrusted files with elevated privileges. Additionally, regular security assessments should include verification that ExifTool installations are current and that temporary file handling processes do not create predictable naming patterns that could be exploited by attackers.