CVE-2017-9893 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 a "User Mode Write AV starting at Xfpx!gffGetFormatInfo+0x0000000000012548."
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Analysis
by VulDB Data Team • 10/23/2019
CVE-2017-9893 represents a critical heap-based buffer overflow vulnerability affecting XnView Classic for Windows version 2.40 and potentially earlier versions. This vulnerability resides within the file processing functionality of the image viewer application, specifically when handling .fpx files which are part of the Microsoft Fax format. The flaw manifests as a user mode write access violation occurring at the Xfpx!gffGetFormatInfo function address 0x0000000000012548, indicating a classic stack-based buffer overflow condition that can be exploited by remote attackers to execute arbitrary code on vulnerable systems.
The technical exploitation of this vulnerability follows a well-documented pattern where attackers craft malicious .fpx files containing oversized data structures that exceed the allocated buffer space within the application's processing pipeline. This type of vulnerability maps directly to CWE-121, which describes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The attack vector is particularly concerning as it requires no user interaction beyond opening the malicious file, making it a prime candidate for drive-by download attacks or social engineering campaigns targeting unsuspecting users.
From an operational impact perspective, successful exploitation of CVE-2017-9893 can result in complete system compromise, allowing attackers to execute malicious code with the privileges of the affected application process. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage, as attackers can leverage the executed code to establish persistent access, escalate privileges, or deploy additional malware payloads. The vulnerability affects systems running Windows operating systems where XnView Classic is installed, creating a significant risk for both enterprise environments and individual users who may encounter malicious .fpx files through email attachments, web downloads, or file sharing networks.
Mitigation strategies for this vulnerability should include immediate patching of the XnView Classic application to version 2.41 or later, which contains the necessary memory bounds checking and buffer overflow protections. Organizations should implement network-based restrictions to block .fpx file types from entering the network perimeter, particularly in email gateways and web proxies. Additionally, application whitelisting solutions can be configured to restrict execution of XnView Classic to trusted environments only. The vulnerability also underscores the importance of regular security assessments and penetration testing to identify similar memory corruption issues in legacy applications, as these types of flaws often persist in older software versions that have not received proper security updates. System administrators should also consider implementing exploit prevention measures such as data execution prevention and address space layout randomization to limit the effectiveness of potential exploitation attempts.