CVE-2017-9912 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!RtlpFreeHeap+0x0000000000000393."
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Analysis
by VulDB Data Team • 10/23/2019
CVE-2017-9912 represents a critical heap-based buffer overflow vulnerability affecting XnView Classic for Windows version 2.40 that demonstrates a fundamental flaw in memory management within the application's handling of .fpx image files. This vulnerability resides within the ntdll component of the Windows operating system, specifically at the RtlpFreeHeap function where faulting address controls branch selection, indicating a sophisticated exploitation vector that leverages the underlying Windows heap management mechanisms. The flaw manifests when the application processes malformed .fpx files, which are used for storing multi-frame images with various compression formats, creating a dangerous condition where attacker-controlled data can manipulate memory allocation and deallocation processes.
The technical exploitation of this vulnerability follows a predictable pattern that aligns with common heap overflow attack methodologies and maps directly to CWE-122, which describes "Heap-based Buffer Overflow" in software systems. When XnView Classic attempts to parse the crafted .fpx file, the malformed data structure causes the application to allocate memory in unexpected ways, leading to a situation where the heap metadata becomes corrupted. This corruption occurs at the heap free function level, where the application's attempt to return memory to the system triggers an unpredictable branch selection mechanism that can be controlled by the attacker through the malformed input data. The vulnerability's classification as a denial of service condition stems from the fact that the heap corruption typically results in application crashes, but the unspecified other impacts suggest potential for more severe consequences including arbitrary code execution.
The operational impact of CVE-2017-9912 extends beyond simple application instability to represent a significant security risk in environments where image processing is common, particularly in enterprise settings where users might encounter malicious attachments or images through email systems, web portals, or file sharing platforms. Attackers exploiting this vulnerability could potentially leverage the heap corruption to execute arbitrary code within the context of the XnView Classic application, which operates with the privileges of the user who launched the application. This vulnerability also aligns with ATT&CK technique T1203, "Exploitation for Client Execution," as it enables attackers to execute malicious code through client-side applications that process image files. The attack surface is particularly concerning given that .fpx files are often encountered in legitimate business scenarios, making social engineering attacks more effective as users are less likely to suspect image files as potential threats.
Mitigation strategies for CVE-2017-9912 should focus on immediate patching of the affected XnView Classic version, as this represents the most effective defense against exploitation. Organizations should implement strict file type filtering at network boundaries and email gateways to prevent .fpx files from entering the enterprise environment. Additionally, users should be educated about the risks of opening image files from untrusted sources, and administrators should consider implementing application whitelisting policies that restrict execution of potentially vulnerable image processing applications. The vulnerability's relationship to heap management issues also suggests that memory protection mechanisms such as Data Execution Prevention and Address Space Layout Randomization should be enabled and properly configured. System monitoring should include detection of abnormal application behavior patterns that might indicate heap corruption, and incident response procedures should be updated to address potential exploitation of this class of vulnerability. Security teams should also consider implementing sandboxing mechanisms for image file processing to contain potential exploitation attempts and prevent lateral movement within the network.