CVE-2018-7729 in Exempi
Summary
by MITRE
An issue was discovered in Exempi through 2.4.4. There is a stack-based buffer over-read in the PostScript_MetaHandler::ParsePSFile() function in XMPFiles/source/FileHandlers/PostScript_Handler.cpp.
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Analysis
by VulDB Data Team • 02/17/2023
The vulnerability identified as CVE-2018-7729 represents a critical stack-based buffer over-read flaw within the Exempi library version 2.4.4 and earlier. This issue manifests in the PostScript_MetaHandler::ParsePSFile() function located within the XMPFiles/source/FileHandlers/PostScript_Handler.cpp source file, where improper input validation leads to memory access violations that can be exploited by malicious actors. The Exempi library serves as a core component for handling XMP metadata in various applications, making this vulnerability particularly concerning for software systems that process document metadata.
The technical nature of this flaw stems from inadequate bounds checking during the parsing of PostScript files, where the application fails to properly validate the size of input data before attempting to read from memory locations. When malformed or excessively large PostScript data is processed, the function attempts to access memory beyond the allocated buffer boundaries, resulting in a buffer over-read condition. This type of vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue that can lead to arbitrary code execution or system instability. The vulnerability is particularly dangerous because it can be triggered through the processing of maliciously crafted PostScript files that contain oversized data structures or malformed metadata.
The operational impact of CVE-2018-7729 extends beyond simple application crashes, as it creates potential entry points for more sophisticated attacks within the software supply chain. Systems that utilize Exempi for metadata processing, including document management platforms, content management systems, and digital asset management tools, become vulnerable to remote code execution when processing untrusted PostScript files. This vulnerability aligns with ATT&CK technique T1203, which involves exploitation of software vulnerabilities for privilege escalation, and can be leveraged by attackers to gain unauthorized access to systems that process document metadata. The flaw can be particularly devastating in enterprise environments where automated metadata extraction processes might inadvertently process malicious files, leading to widespread system compromise.
Mitigation strategies for this vulnerability require immediate patching of the Exempi library to version 2.4.5 or later, which contains the necessary fixes for the buffer over-read condition. Organizations should implement comprehensive input validation measures that enforce strict size limitations on PostScript file processing, combined with sandboxing techniques to isolate metadata processing functions. Additionally, security teams should deploy network monitoring solutions that can detect unusual file processing patterns and implement strict file type validation to prevent the processing of potentially malicious PostScript files. The remediation process should include thorough vulnerability scanning of all systems that utilize Exempi, followed by systematic patch deployment and configuration hardening to prevent exploitation attempts. Security professionals should also consider implementing application whitelisting controls that restrict the execution of untrusted metadata processing operations, thereby reducing the attack surface for this and similar buffer overflow vulnerabilities.