CVE-2017-10737 in XnView Classic
Summary
by MITRE
XnView Classic for Windows Version 2.40 allows attackers to execute arbitrary code or cause a denial of service via a crafted .rle file, related to a "User Mode Write AV starting at ntdll_77df0000!RtlpCoalesceFreeBlocks+0x00000000000002e6."
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Analysis
by VulDB Data Team • 07/01/2020
The vulnerability identified as CVE-2017-10737 affects XnView Classic for Windows version 2.40, presenting a critical security risk that can be exploited through manipulation of .rle image files. This flaw represents a classic buffer overflow condition that occurs within the application's handling of raster image files, specifically those using the Run-Length Encoded format. The vulnerability manifests when the application processes a specially crafted .rle file that contains malformed data structures, leading to unpredictable behavior in the memory management subsystem. The attack vector is particularly concerning because it leverages the application's legitimate file parsing functionality to achieve unauthorized code execution or system instability.
The technical root cause of this vulnerability lies in improper bounds checking and memory management within the XnView Classic image processing engine. When the application encounters a malformed .rle file, the parsing routine fails to validate the data structure boundaries before attempting to write to memory locations. The error message references ntdll_77df0000!RtlpCoalesceFreeBlocks+0x00000000000002e6, indicating that the crash occurs within the Windows kernel's memory management functions, specifically during the process of coalescing free memory blocks. This suggests that the buffer overflow has corrupted the heap memory management structures, leading to a write access violation that terminates the application process or potentially allows for arbitrary code execution. The vulnerability is classified as a user-mode write access violation, which aligns with CWE-121, heap-based buffer overflow conditions that occur in the application's memory management routines.
The operational impact of this vulnerability extends beyond simple denial of service, as it provides attackers with potential paths to execute malicious code on targeted systems. An attacker who can convince a user to open a specially crafted .rle file through XnView Classic could gain remote code execution privileges, potentially leading to full system compromise. This represents a significant risk in environments where users may encounter untrusted image files through email attachments, web downloads, or file sharing networks. The vulnerability is particularly dangerous in enterprise environments where image viewing applications are commonly used for document review, image processing, and media management tasks. The exploitability factor is enhanced by the fact that the attack requires minimal user interaction beyond opening the malicious file, making it a prime target for social engineering campaigns and automated exploitation attempts. The flaw also demonstrates poor input validation practices that could potentially affect other file formats processed by the same application, increasing the attack surface.
Mitigation strategies for CVE-2017-10737 should focus on immediate patch deployment and operational security measures. The primary solution involves updating to a patched version of XnView Classic that addresses the buffer overflow conditions in the .rle file parser. Organizations should also implement application whitelisting policies that restrict execution of image viewing applications to trusted environments, particularly in high-security contexts. Network-based protections such as email filtering and web proxy scanning should be enhanced to detect and block potentially malicious .rle files before they reach end users. Additionally, system administrators should consider implementing sandboxing techniques for image viewing applications to limit the potential impact of successful exploits. The vulnerability highlights the importance of input validation and memory safety practices, aligning with ATT&CK technique T1203 for legitimate program execution and T1059 for command and scripting interpreter usage. Regular security assessments and penetration testing should include evaluation of image processing applications to identify similar buffer overflow conditions that could be exploited in similar ways.