CVE-2016-7976 in Ghostscript
Summary
by MITRE
The PS Interpreter in Ghostscript 9.18 and 9.20 allows remote attackers to execute arbitrary code via crafted userparams.
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Analysis
by VulDB Data Team • 12/15/2022
The vulnerability identified as CVE-2016-7976 represents a critical remote code execution flaw within the PostScript interpreter component of Ghostscript versions 9.18 and 9.20. This issue resides in the handling of user parameters during the processing of PostScript documents, creating an avenue for attackers to inject and execute malicious code on systems running affected versions of the software. The vulnerability specifically targets the PS interpreter which is responsible for interpreting and rendering PostScript language commands, making it a core component susceptible to exploitation through crafted input parameters.
The technical flaw manifests when the PS interpreter processes userparams, which are parameters passed to the interpreter during document processing. Attackers can manipulate these parameters to trigger unintended code execution paths within the interpreter's codebase. The vulnerability stems from inadequate input validation and sanitization of user-provided parameters, allowing malicious payloads to bypass normal execution boundaries. This type of vulnerability aligns with CWE-787, which describes out-of-bounds writes, and CWE-121, which covers stack-based buffer overflow conditions. The flaw essentially allows attackers to manipulate the interpreter's internal state through carefully crafted parameter sequences that can lead to arbitrary code execution in the context of the running process.
The operational impact of this vulnerability is severe as it enables remote attackers to execute arbitrary code on systems without requiring local access or authentication. This makes it particularly dangerous in environments where Ghostscript is used to process untrusted documents, such as web applications, email servers, or document conversion services. The vulnerability can be exploited through various attack vectors including web-based document processing, email attachments, or file sharing systems where users might unknowingly open malicious PostScript files. The exploitation capability extends to privilege escalation scenarios where attackers could potentially gain system-level control, making this vulnerability particularly attractive to threat actors seeking persistent access to target systems.
Mitigation strategies for CVE-2016-7976 should prioritize immediate patching of affected Ghostscript installations to versions that contain fixes for the PS interpreter parameter handling. Organizations should implement network segmentation and access controls to limit exposure of systems running Ghostscript to untrusted inputs. Input validation and sanitization measures should be strengthened to prevent malformed parameters from reaching the interpreter component. Security monitoring should be enhanced to detect anomalous behavior patterns that might indicate exploitation attempts. The vulnerability's characteristics align with ATT&CK technique T1059.007, which covers scripting languages, and T1203, which describes exploitation for privilege escalation. Regular security assessments and vulnerability scanning should be conducted to identify systems running outdated versions of Ghostscript that may be susceptible to similar vulnerabilities in the broader ecosystem.