CVE-2013-5653 in Ghostscript
Summary
by MITRE
The getenv and filenameforall functions in Ghostscript 9.10 ignore the "-dSAFER" argument, which allows remote attackers to read data via a crafted postscript file.
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Analysis
by VulDB Data Team • 09/04/2020
The vulnerability identified as CVE-2013-5653 represents a critical security flaw in Ghostscript version 9.10 that undermines the software's core security mechanisms. This issue affects the getenv and filenameforall functions within the PostScript interpreter, which are fundamental components responsible for handling environment variables and file operations. The vulnerability stems from the software's failure to properly respect the "-dSAFER" security flag that should restrict access to system resources and prevent unauthorized file operations. When this flag is ignored, it creates a pathway for malicious actors to bypass security controls that are designed to isolate the PostScript interpreter from the underlying operating system. The flaw specifically impacts systems where Ghostscript is used to process untrusted PostScript or PDF files, making it particularly dangerous in environments where document processing occurs without proper sandboxing.
The technical implementation of this vulnerability exploits the inherent design of Ghostscript's security model where the "-dSAFER" parameter is intended to disable potentially dangerous operations such as file system access, environment variable reading, and network communications. However, the getenv and filenameforall functions fail to check for this security flag's presence before executing their respective operations, allowing attackers to craft malicious PostScript code that can read system environment variables or enumerate file system contents. This behavior directly violates the principle of least privilege that should govern all system operations, as it enables unauthorized access to sensitive information that would normally be restricted. The vulnerability is particularly insidious because it operates at the interpreter level rather than at the application level, meaning that even properly configured applications using Ghostscript could be compromised if they process untrusted input without additional safeguards.
The operational impact of CVE-2013-5653 extends beyond simple information disclosure, as it provides attackers with valuable reconnaissance data that can be used to plan more sophisticated attacks. By reading environment variables, attackers can discover system configurations, user permissions, and potentially sensitive information stored in environment variables such as database connection strings or API keys. The filenameforall function's inability to respect security restrictions allows for directory traversal and file enumeration attacks, potentially exposing the entire file system structure to unauthorized parties. This vulnerability is especially concerning in web applications that use Ghostscript for document conversion, as it can be exploited through crafted PDF or PostScript files uploaded to servers. The attack surface is further expanded when considering that many organizations rely on Ghostscript for automated document processing, making the exploitation of this vulnerability potentially widespread and difficult to detect.
Security mitigations for CVE-2013-5653 should focus on immediate remediation through software updates to versions that properly implement the "-dSAFER" security flag. Organizations should also implement additional layers of protection such as deploying sandboxing solutions that isolate Ghostscript processes from the host system, implementing strict input validation for all PostScript and PDF files, and configuring network firewalls to limit access to systems running Ghostscript. The vulnerability aligns with CWE-254, which describes security vulnerabilities related to improper handling of security features, and maps to ATT&CK technique T1059.007 for PostScript execution and T1078 for valid accounts usage. System administrators should also consider implementing monitoring solutions that can detect unusual file access patterns or environment variable reads that might indicate exploitation attempts. Regular security audits and penetration testing should be conducted to ensure that all systems using Ghostscript are properly configured and that no other similar vulnerabilities exist in the software stack. The incident highlights the critical importance of proper security flag implementation and the need for comprehensive security testing of interpreter-based systems that handle untrusted input data.