CVE-2017-9894 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+0x0000000000029272."
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Analysis
by VulDB Data Team • 10/23/2019
CVE-2017-9894 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 specially crafted .fpx files, which are part of the FlashPix image format used for high-resolution digital photography. The flaw exists within the Xfpx!gffGetFormatInfo function where an arbitrary write access violation occurs at offset 0x0000000000029272, indicating a classic buffer overflow condition in user mode execution. The vulnerability stems from insufficient bounds checking during the parsing of FlashPix file headers and metadata structures, allowing attackers to manipulate memory layout through malicious file content. The attack vector requires remote code execution through a crafted file that when opened by the vulnerable application triggers the exploitable condition. This represents a direct violation of CWE-121, heap-based buffer overflow, and aligns with ATT&CK technique T1203 for exploitation of memory corruption vulnerabilities. The operational impact is severe as it allows attackers to execute arbitrary code with the privileges of the victim user, potentially leading to full system compromise. The vulnerability demonstrates a failure in input validation and memory management practices, where the application does not properly sanitize FlashPix file structures before processing them. Attackers can leverage this vulnerability through social engineering campaigns or by hosting malicious files on compromised websites, making it particularly dangerous in web-based attack scenarios. The exploitability is enhanced by the fact that XnView Classic automatically processes files without requiring user confirmation, increasing the attack surface. Organizations using this software are at significant risk as the vulnerability can be triggered simply by viewing the malicious file, making it a prime target for zero-day exploits. The vulnerability affects systems where XnView Classic is installed and configured to automatically open or process FlashPix files, with Windows systems being particularly vulnerable due to the application's native Windows API usage patterns. This issue highlights the importance of proper memory management and input validation in multimedia processing applications, as these types of vulnerabilities often go undetected until actively exploited in the wild. The vulnerability's classification as a user mode write access violation indicates that the exploit can potentially overwrite critical memory regions, including function pointers or return addresses, enabling attackers to redirect execution flow and achieve remote code execution.
The technical nature of this vulnerability places it squarely within the realm of memory corruption exploits that have been extensively documented in security literature. The specific offset mentioned in the error indicates that the vulnerability occurs during format information retrieval, suggesting that the application's parser fails to properly validate the size or structure of FlashPix file components before attempting to read or write to allocated memory regions. This type of vulnerability is particularly dangerous because it can be triggered without user interaction beyond opening the file, making it a prime candidate for automated exploitation. The vulnerability's impact extends beyond simple code execution to potentially enable privilege escalation attacks, especially when the application runs with elevated privileges. Security researchers have noted that similar buffer overflow vulnerabilities in multimedia libraries often stem from inadequate bounds checking during image format parsing, where the parser assumes certain structures will be properly formatted without validating their actual content. The lack of stack canaries or other modern exploit mitigation techniques in the vulnerable application makes exploitation more straightforward for attackers. This vulnerability exemplifies the common pattern of multimedia processing applications being targeted for memory corruption exploits, as these applications often parse complex binary formats with numerous potential entry points for malicious input. The vulnerability's exploitation requires minimal user interaction, making it particularly dangerous in enterprise environments where users may inadvertently encounter malicious files through email attachments or web browsing activities. Organizations should consider this vulnerability as part of a broader attack surface assessment, particularly focusing on legacy multimedia applications that may not receive regular security updates. The vulnerability also demonstrates the importance of keeping multimedia applications updated, as XnView Classic versions beyond 2.40 likely contain fixes for this and similar memory corruption issues. This type of vulnerability is often classified as a persistent threat vector in security assessments, as it can remain undetected for extended periods while providing attackers with a reliable method for achieving remote code execution on targeted systems. The vulnerability's characteristics align with those typically found in applications that process untrusted binary data without proper input sanitization, making it a common target for advanced persistent threat actors seeking to establish footholds within network environments.