CVE-2017-9899 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+0x000000000002e388."
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Analysis
by VulDB Data Team • 10/23/2019
CVE-2017-9899 represents a critical remote code execution vulnerability affecting XnView Classic for Windows version 2.40 and potentially earlier versions. This vulnerability stems from improper input validation within the application's handling of .fpx file format, which is a proprietary format used by XnView for storing image data. The flaw manifests when the application processes a specially crafted .fpx file that contains malicious data structures designed to exploit memory corruption issues during file parsing operations. 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 attackers to execute arbitrary code with the privileges of the affected application.
The technical exploitation of this vulnerability follows a well-established pattern of memory corruption attacks that aligns with common CWE classifications including CWE-121, CWE-125, and CWE-787, which describe stack-based buffer overflows, out-of-bounds reads, and buffer overflow conditions respectively. The attack vector involves remote exploitation through a maliciously crafted .fpx file, making it particularly dangerous as it can be delivered through email attachments, web downloads, or file sharing platforms without requiring user interaction beyond opening the file. The vulnerability's location within the Xfpx!gffGetFormatInfo function suggests that the application fails to properly validate the size or structure of data elements within the .fpx file format, allowing attackers to manipulate memory layout and potentially redirect execution flow to malicious code injected into the application's memory space. This type of vulnerability is categorized under the ATT&CK framework as T1203 - Exploitation for Client Execution, where adversaries leverage application vulnerabilities to execute malicious code on targeted systems.
The operational impact of CVE-2017-9899 extends beyond simple code execution, as successful exploitation can lead to complete system compromise and persistent access for threat actors. An attacker who successfully exploits this vulnerability can gain the same privileges as the XnView application, which typically runs with user-level privileges but could potentially be elevated if the application is running with administrative rights. The vulnerability's remote nature means that attackers can exploit it without physical access to the target system, making it particularly attractive for large-scale attacks. Organizations using XnView Classic for image processing and viewing operations face significant risk, as the application is commonly used in environments where users may encounter untrusted image files from various sources. The exploitability of this vulnerability is further enhanced by the fact that .fpx files are legitimate image formats, making them less suspicious to end users and security tools that might not flag them as malicious.
Mitigation strategies for CVE-2017-9899 should focus on immediate remediation and long-term defensive measures. The most effective immediate solution is to update to a patched version of XnView Classic, as the vendor has released updates addressing this specific vulnerability. Organizations should implement strict file validation and scanning procedures for all image files, particularly those received from external sources or untrusted networks. Network-based defenses should include filtering of .fpx files at perimeter defenses and implementing application whitelisting to prevent execution of untrusted applications. System hardening measures should include disabling unnecessary file format support within applications, implementing address space layout randomization, and using stack canaries to make exploitation more difficult. Additionally, security awareness training should emphasize the dangers of opening unknown image files, as social engineering remains a common initial attack vector for exploiting such vulnerabilities. The vulnerability also highlights the importance of input validation and memory safety practices in software development, particularly for applications handling untrusted data formats, which aligns with industry best practices outlined in secure coding standards and guidelines such as those provided by the CERT/CC and OWASP foundations.