CVE-2017-9898 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+0x0000000000004cbb."
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Analysis
by VulDB Data Team • 10/23/2019
The vulnerability identified as CVE-2017-9898 represents a critical remote code execution flaw in XnView Classic for Windows version 2.40 that stems from improper handling of specially crafted .fpx files. This issue falls under the category of heap-based buffer overflow conditions where the application fails to properly validate input data during the processing of Fast Picture Exchange format files. The vulnerability specifically manifests as a user mode write access violation occurring at the Xfpx+0x0000000000004cbb memory offset, indicating a precise location within the application's memory management routines where the overflow occurs. Such a flaw represents a classic example of a memory corruption vulnerability that can be exploited to gain arbitrary code execution privileges.
The technical exploitation of this vulnerability relies on the attacker crafting a malicious .fpx file that triggers the buffer overflow condition when XnView Classic attempts to parse and render the image file. This process typically involves manipulating the file's header structures and data segments to overwrite adjacent memory locations, potentially leading to stack corruption or heap corruption patterns that can be leveraged for code execution. The vulnerability's classification aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read vulnerabilities that can lead to memory corruption. 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.
From an operational impact perspective, successful exploitation of CVE-2017-9898 can result in complete system compromise, allowing attackers to execute arbitrary code with the privileges of the affected user. This vulnerability can be particularly dangerous in enterprise environments where users may inadvertently open malicious files from email attachments, web downloads, or compromised websites. The vulnerability's presence in a widely used image viewing application means that exploitation can occur across various attack surfaces, from individual user endpoints to corporate networks where image files are commonly shared. This flaw directly maps to several ATT&CK techniques including T1059 for command and scripting interpreter usage and T1068 for exploit for privilege escalation, as the initial code execution can potentially be leveraged for further system compromise.
The mitigation strategies for this vulnerability primarily focus on immediate patching and updating of XnView Classic to versions that address the buffer overflow condition. Organizations should implement strict file validation policies that prevent execution of untrusted image files from unknown sources, particularly in environments where users may encounter malicious attachments or downloads. Network-based mitigations can include implementing content filtering solutions that block .fpx file types or scanning image files for known malicious patterns before allowing access. Additionally, system hardening measures such as enabling address space layout randomization and data execution prevention can make exploitation more difficult, though these protections are not foolproof against sophisticated attackers. Security teams should also consider implementing user education programs to raise awareness about the dangers of opening untrusted image files, as this vulnerability can be effectively exploited through social engineering techniques that trick users into opening malicious files.