CVE-2017-9897 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+0x000000000000dcab."
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Analysis
by VulDB Data Team • 10/23/2019
CVE-2017-9897 represents a critical heap-based buffer overflow vulnerability affecting XnView Classic for Windows version 2.40 and potentially earlier versions. This vulnerability manifests when the application processes maliciously crafted .fpx files, which are part of the FlashPix image format. The flaw occurs within the Xfpx component of the software, specifically at offset 0x000000000000dcab in the user mode write access violation. The vulnerability stems from inadequate input validation and memory management within the image parsing routine, allowing attackers to manipulate memory structures through carefully constructed file headers and metadata.
The technical exploitation of this vulnerability leverages a classic buffer overflow condition where insufficient bounds checking permits data to be written beyond allocated memory boundaries. This allows attackers to overwrite adjacent memory locations including return addresses and function pointers, enabling arbitrary code execution with the privileges of the victim user. The vulnerability is particularly dangerous because it operates within a widely used image viewer application, making it accessible to attackers through common attack vectors such as email attachments, web downloads, or malicious websites. The attack requires no special privileges to initiate, as the vulnerability exists in the application's processing of untrusted input data.
From an operational perspective, this vulnerability poses significant risks to enterprise environments where XnView Classic is deployed, as it can be exploited through social engineering campaigns targeting end users. The attack surface extends beyond individual user systems to include corporate networks where image viewing applications are commonly used for document review and file sharing. The exploitability is enhanced by the fact that .fpx files are less commonly scrutinized than executable formats, making them effective attack vectors. Security professionals should note that this vulnerability aligns with CWE-121, heap-based buffer overflow, and maps to ATT&CK technique T1203, Exploitation for Client Execution, which describes how attackers use vulnerabilities to execute code on target systems through application exploitation.
Mitigation strategies for CVE-2017-9897 should prioritize immediate patching of affected XnView Classic installations, as the vendor has released updates addressing the heap overflow condition. Organizations should implement restrictive file type handling policies, particularly disabling automatic processing of .fpx files in enterprise environments. Network-based defenses can include content filtering solutions that block suspicious file types and implement deep packet inspection for malformed image files. Additionally, user education programs should emphasize the dangers of opening untrusted image files, while system hardening measures such as application whitelisting and sandboxing can provide additional defense layers. The vulnerability also highlights the importance of regular security assessments of image processing libraries and applications, as similar issues may exist in other components of the software ecosystem.