CVE-2017-6196 in Ghostscript
Summary
by MITRE
Multiple use-after-free vulnerabilities in the gx_image_enum_begin function in base/gxipixel.c in Ghostscript before ecceafe3abba2714ef9b432035fe0739d9b1a283 allow remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact via a crafted PostScript document.
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Analysis
by VulDB Data Team • 08/18/2020
The vulnerability identified as CVE-2017-6196 represents a critical use-after-free flaw in Ghostscript's graphics processing subsystem, specifically within the gx_image_enum_begin function located in base/gxipixel.c. This vulnerability affects Ghostscript versions prior to the commit ecceafe3abba2714ef9b432035fe0739d9b1a283, creating a significant security risk for systems that process PostScript documents. The flaw stems from improper memory management where freed memory locations are accessed after the gx_image_enum_begin function has been invoked with maliciously crafted PostScript input, leading to unpredictable behavior and potential system compromise.
The technical implementation of this vulnerability involves a classic use-after-free condition where the application allocates memory for image enumeration structures but fails to properly validate or sanitize input parameters from PostScript documents. When a crafted document triggers the gx_image_enum_begin function, the memory management routines may execute operations on already freed memory blocks, resulting in heap corruption. This memory corruption can manifest as application crashes during document processing or potentially enable more sophisticated attack vectors depending on the execution environment and memory layout. The vulnerability operates at the intersection of graphics processing and memory safety, making it particularly dangerous in server environments where Ghostscript processes untrusted documents from multiple sources.
The operational impact of CVE-2017-6196 extends beyond simple denial of service to potentially enable more severe consequences including remote code execution and system compromise. Attackers can leverage this vulnerability by constructing malicious PostScript documents that, when processed by vulnerable Ghostscript implementations, trigger the use-after-free condition. The vulnerability affects a wide range of systems including web servers, print servers, and document processing applications that rely on Ghostscript for rendering PostScript content. This creates a substantial risk for organizations that process untrusted document uploads or have systems that automatically render PostScript documents, as the attack surface is broad and the exploitation potential is significant.
Mitigation strategies for CVE-2017-6196 should prioritize immediate patching of affected Ghostscript installations to the version containing the fix referenced by the commit ecceafe3abba2714ef9b432035fe0739d9b1a283. Organizations should also implement network segmentation and access controls to limit exposure of systems running Ghostscript to untrusted inputs. Additional defensive measures include deploying sandboxing mechanisms for document processing, implementing strict input validation for PostScript content, and monitoring for unusual application behavior that may indicate exploitation attempts. The vulnerability aligns with CWE-416, which specifically addresses use-after-free errors, and could potentially map to ATT&CK techniques involving privilege escalation and code execution through memory corruption vulnerabilities. Security teams should also consider implementing automated vulnerability scanning to identify systems running vulnerable versions and establish incident response procedures for potential exploitation attempts.