CVE-2018-15911 in Ghostscript
Summary
by MITRE
In Artifex Ghostscript 9.23 before 2018-08-24, attackers able to supply crafted PostScript could use uninitialized memory access in the aesdecode operator to crash the interpreter or potentially execute code.
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Analysis
by VulDB Data Team • 05/06/2023
The vulnerability identified as CVE-2018-15911 represents a critical memory safety issue within Artifex Ghostscript version 9.23 and earlier releases. This flaw manifests in the aesdecode operator which is responsible for handling Advanced Encryption Standard decryption operations within the PostScript interpreter. The vulnerability arises from improper initialization of memory variables during the decryption process, creating a scenario where uninitialized memory segments are accessed by the interpreter. The affected environment specifically occurs when Ghostscript processes crafted PostScript files that contain maliciously constructed aesdecode operations, enabling attackers to manipulate the interpreter's memory state in ways that were not anticipated during normal operation.
The technical exploitation of this vulnerability stems from a classic uninitialized memory access flaw that can be classified under CWE-457, which describes the use of uninitialized variables in security-sensitive contexts. When an attacker supplies a malicious PostScript file containing crafted aesdecode operations, the interpreter attempts to process these commands without proper initialization of memory buffers. This creates a condition where the program may read from memory locations that contain arbitrary data, potentially leading to unpredictable behavior. The uninitialized memory access can cause the interpreter to crash immediately upon encountering the malformed input, or in more sophisticated attack scenarios, the attacker may be able to manipulate the memory contents to achieve code execution within the context of the Ghostscript process.
From an operational impact perspective, this vulnerability presents significant risks to organizations that rely on Ghostscript for document processing and rendering operations. The attack vector involves the delivery of malicious PostScript files through various means including email attachments, web downloads, or file sharing platforms, making it particularly dangerous in enterprise environments where document processing is common. The potential for remote code execution means that an attacker could gain unauthorized access to systems running vulnerable Ghostscript versions, potentially leading to full system compromise. The vulnerability affects not only direct installations but also applications that depend on Ghostscript as a backend component, amplifying the attack surface considerably. Organizations using Ghostscript for rendering PDFs, processing print jobs, or handling document conversion operations are all at risk when running vulnerable versions.
The mitigation strategy for this vulnerability requires immediate patching of all affected Ghostscript installations to versions released after 2018-08-24, which contain the necessary memory initialization fixes. System administrators should implement a comprehensive patch management process to ensure all instances of Ghostscript are updated promptly, particularly in environments where document processing occurs. Additionally, organizations should consider implementing input validation measures that can detect and block suspicious PostScript constructs before they reach the interpreter. Network segmentation and application whitelisting can provide additional defense-in-depth layers to prevent exploitation attempts. The vulnerability also highlights the importance of maintaining updated security practices and conducting regular vulnerability assessments of third-party components used in document processing pipelines. Security monitoring should include detection of unusual memory access patterns and potential exploitation attempts targeting similar uninitialized memory vulnerabilities in other software components.
This vulnerability aligns with several ATT&CK techniques including T1059.007 for PostScript execution and T1068 for exploit for privilege escalation. The attack chain typically begins with initial access through malicious document delivery, followed by exploitation of the uninitialized memory access to achieve code execution. The remediation process should include not only patching but also security awareness training for personnel who may encounter suspicious document attachments, as social engineering remains a common delivery method for such attacks. Organizations should also consider implementing sandboxing mechanisms for document processing to isolate potentially malicious content from the main system environment.