CVE-2010-4820 in Ghostscript
Summary
by MITRE
Untrusted search path vulnerability in Ghostscript 8.62 allows local users to execute arbitrary PostScript code via a Trojan horse Postscript library file in Encoding/ under the current working directory, a different vulnerability than CVE-2010-2055.
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Analysis
by VulDB Data Team • 04/03/2022
The vulnerability identified as CVE-2010-4820 represents a critical untrusted search path issue within Ghostscript version 8.62 that enables local privilege escalation through malicious PostScript library manipulation. This flaw resides in the software's handling of library file resolution during PostScript processing operations, specifically when the application searches for encoding files within the Encoding/ directory. The vulnerability stems from the application's insecure direct object reference pattern where it fails to validate the authenticity and origin of library files loaded from user-accessible directories, creating a pathway for attackers to execute arbitrary code through carefully crafted malicious files.
The technical exploitation of this vulnerability occurs when a local attacker places a Trojan horse PostScript library file within the Encoding/ subdirectory of the current working directory. When Ghostscript processes PostScript documents that reference encoding files, it traverses the file system using a predictable search order that includes the current working directory before system directories. This search path order allows the malicious library to be loaded instead of the legitimate system library, effectively hijacking the application's execution flow. The vulnerability is classified under CWE-427 Uncontrolled Search Path Element, which specifically addresses situations where applications search for resources using paths that can be manipulated by attackers, and it aligns with ATT&CK technique T1068 for locally executed malicious code.
The operational impact of this vulnerability extends beyond simple code execution to potentially enable full system compromise when combined with other attack vectors. Local attackers can leverage this weakness to bypass security controls that might otherwise prevent code execution, particularly in environments where Ghostscript is used for document processing or rendering. The vulnerability affects systems where users have write access to the current working directory or where the application is executed in contexts where directory traversal attacks are feasible. Attackers can craft malicious PostScript files that, when processed by the vulnerable Ghostscript, trigger the loading of the malicious library and subsequently execute arbitrary code with the privileges of the Ghostscript process, which may run with elevated permissions depending on system configuration.
Mitigation strategies for CVE-2010-4820 should focus on both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. The most effective immediate solution involves upgrading to a patched version of Ghostscript that addresses the untrusted search path issue through proper library validation and secure path resolution. Organizations should implement strict access controls to prevent unauthorized modifications of the Ghostscript installation directories and related encoding files. Additionally, security configurations should enforce secure library loading practices by using absolute paths for library references, implementing proper file permission controls, and ensuring that the application's search path prioritizes system directories over user-accessible locations. System administrators should also consider implementing monitoring solutions that can detect unauthorized modifications to critical library files and establish baseline configurations that prevent the execution of unsigned or untrusted code within the application's operational environment.