CVE-2017-9902 in XnView Classic
Summary
by MITRE
XnView Classic for Windows Version 2.40 allows remote attackers to execute code via a crafted .fpx file, related to "Data from Faulting Address controls Code Flow starting at Xfpx!gffGetFormatInfo+0x0000000000020e91."
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Analysis
by VulDB Data Team • 10/23/2019
CVE-2017-9902 represents a critical remote code execution vulnerability affecting XnView Classic for Windows version 2.40 and potentially earlier versions. This vulnerability resides within the handling of .fpx file format processing, which is a proprietary format used by XnView for storing image data with additional metadata. The flaw manifests when the application processes a specially crafted .fpx file that contains malicious data structures designed to exploit memory corruption issues during the image parsing process. The vulnerability specifically occurs at the Xfpx!gffGetFormatInfo function where faulting address controls code flow, indicating a classic buffer overflow or memory corruption scenario that can be leveraged by remote attackers to gain arbitrary code execution privileges on the target system.
The technical nature of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read vulnerabilities. The exploitation mechanism involves manipulating the data structures within the .fpx file format to overwrite critical memory locations, particularly around the function pointer or return address of the gffGetFormatInfo routine. This type of vulnerability is particularly dangerous because it can be triggered through a simple file attachment or download operation, making it suitable for phishing attacks or malicious website exploitation. The attack vector requires no user interaction beyond opening the malicious file, as the vulnerability is triggered during the automatic parsing and display of image files by the application.
From an operational impact perspective, this vulnerability creates significant risk for end users and organizations that rely on XnView Classic for image management and viewing. The remote code execution capability means that attackers can potentially install malware, establish backdoors, or completely compromise the affected system without user awareness. The vulnerability affects systems where XnView Classic is installed and actively processes image files, including desktop environments, file servers, and any system that might encounter .fpx files through normal operations. Attackers can leverage this vulnerability through various delivery methods including email attachments, compromised websites, or file sharing platforms where .fpx files might be encountered. The exploitation process typically follows the ATT&CK technique T1203, which involves gaining access through execution of malicious code, and T1059, which covers command and scripting interpreter usage for persistence.
Organizations should implement immediate mitigations including disabling the processing of .fpx files in XnView Classic or updating to the latest version where this vulnerability has been patched. The recommended approach involves either removing the vulnerable file format handler entirely or ensuring that all users have the patched version of the software. System administrators should also consider implementing network-based restrictions that prevent the automatic execution of potentially malicious image files and should monitor for any suspicious file access patterns. Additionally, security awareness training should emphasize the dangers of opening unknown image files, particularly those from untrusted sources, as this vulnerability can be exploited through social engineering attacks. The patching process requires careful testing to ensure that legitimate functionality is not disrupted while addressing the memory corruption issues that enable the code execution exploit.