CVE-2017-9909 in XnView Classic
Summary
by MITRE
XnView Classic for Windows Version 2.40 allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted .fpx file, related to "Data from Faulting Address controls Branch Selection starting at ntdll_77df0000!RtlAddAccessAllowedAce+0x000000000000027a."
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Analysis
by VulDB Data Team • 10/23/2019
The vulnerability identified as CVE-2017-9909 affects XnView Classic for Windows version 2.40 and represents a critical remote code execution flaw that can be exploited through maliciously crafted .fpx files. This vulnerability resides within the application's handling of specific file format structures and demonstrates a classic buffer overflow condition that occurs during the processing of faulting addresses within the Windows ntdll library. The flaw manifests when the application attempts to parse malformed .fpx files, which are used for storing image data in the FlashPix format. The specific faulting address mentioned in the vulnerability description points to ntdll_77df0000!RtlAddAccessAllowedAce+0x000000000000027a, indicating that the vulnerability is directly related to Windows access control list manipulation functions within the native runtime library.
The technical exploitation of this vulnerability involves attackers crafting specially designed .fpx files that trigger memory corruption during the image parsing process. When XnView Classic attempts to process these malicious files, the application's failure handling mechanisms become compromised, leading to unpredictable behavior that can result in system crashes or potentially allow attackers to execute arbitrary code with the privileges of the affected user. The vulnerability's classification as a denial of service condition stems from the fact that the application becomes unresponsive or terminates unexpectedly when encountering these malformed files, while the potential for unspecified other impacts suggests that more severe consequences could occur depending on the execution environment and system configuration. This flaw operates at the intersection of file format parsing and memory management, where improper input validation leads to direct memory corruption.
The operational impact of CVE-2017-9909 extends beyond simple application instability, as it represents a significant security risk for users who may unknowingly open malicious files through XnView Classic. Attackers could leverage this vulnerability in various attack scenarios including phishing campaigns, malicious file sharing, or supply chain compromises where infected .fpx files are embedded within larger packages. The vulnerability affects systems running Windows operating systems and presents a particular concern for enterprise environments where image viewing applications are commonly used for document review and file sharing. Organizations using XnView Classic in production environments face potential exposure to remote exploitation, with the risk of unauthorized system access, data exfiltration, or further lateral movement within compromised networks. The vulnerability's exploitation requires minimal user interaction, as simply opening the malicious file within the application triggers the exploit.
Mitigation strategies for CVE-2017-9909 should focus on immediate patch management and application hardening measures. The primary recommendation involves upgrading to a patched version of XnView Classic that addresses the file format parsing vulnerability and implements proper input validation for .fpx files. Organizations should also consider implementing file extension filtering and content inspection mechanisms to prevent execution of potentially malicious image files. Network-based mitigations can include firewall rules that restrict access to .fpx file types or content filtering solutions that scan image files for known malicious patterns. Additionally, users should be educated about the risks of opening untrusted image files and the importance of keeping software updated. From a security controls perspective, this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a typical attack vector that could be mapped to ATT&CK technique T1203, involving the use of malicious files to gain system access through application vulnerabilities. The vulnerability demonstrates the importance of robust input validation and proper error handling in image processing libraries, particularly those that interface with Windows system libraries such as ntdll.