CVE-2017-8826 in Image Viewer
Summary
by MITRE
FastStone Image Viewer 6.2 has a "User Mode Write AV" issue, possibly related to the jpeg_mem_term function in jmemnobs.c in libjpeg. This issue can be triggered by a malformed JPEG file that is mishandled by FSViewer.exe. Attackers could exploit this issue for DoS (Access Violation) or possibly unspecified other impact.
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Analysis
by VulDB Data Team • 10/22/2019
The vulnerability identified as CVE-2017-8826 represents a critical memory corruption issue within FastStone Image Viewer version 6.2 that stems from improper handling of malformed JPEG files. This flaw manifests as a User Mode Write Access Violation, indicating that the application attempts to write to memory locations that are either protected or invalid during the processing of corrupted image data. The root cause is traced to the jpeg_mem_term function located in jmemnobs.c within the libjpeg library, which serves as the underlying JPEG decoding component for the image viewer application.
The technical exploitation of this vulnerability occurs when FSViewer.exe encounters a specially crafted malformed JPEG file that triggers an abnormal memory access pattern during the decompression process. When the application attempts to terminate memory management operations through jpeg_mem_term, it encounters corrupted memory state or invalid pointers that result in an access violation crash. This behavior aligns with CWE-125: Out-of-bounds Read and CWE-787: Out-of-bounds Write, both of which describe memory safety issues that can lead to arbitrary code execution or denial of service conditions. The vulnerability operates at the application level where the image viewer fails to properly validate input data before processing, creating a path for malicious actors to inject malformed data that triggers the memory corruption.
The operational impact of this vulnerability extends beyond simple denial of service, as it presents potential for more severe consequences within the target system. When exploited, the access violation causes FSViewer.exe to crash and terminate unexpectedly, disrupting user workflows and potentially leading to data loss if the application was in the middle of processing important image files. However, the vulnerability's potential for exploitation goes beyond simple crashes, as it could be leveraged to execute arbitrary code on the target system through techniques that map to ATT&CK tactic TA0005: Defense Evasion and TA0002: Execution. The memory corruption aspect suggests that sophisticated attackers could potentially use this flaw as part of a broader exploitation chain to achieve privilege escalation or system compromise.
Mitigation strategies for CVE-2017-8826 should focus on both immediate remediation and long-term defensive measures. The most direct solution involves updating to a patched version of FastStone Image Viewer that addresses the memory handling issues in the libjpeg component. System administrators should implement application whitelisting policies to restrict execution of potentially vulnerable applications, particularly in enterprise environments where image viewing applications may be used extensively. Network-based defenses such as web application firewalls and content filtering systems can help prevent malicious JPEG files from reaching end users, while endpoint protection solutions should monitor for suspicious file processing behaviors that might indicate exploitation attempts. Additionally, users should be educated about the risks of opening untrusted image files and encouraged to maintain current software versions to minimize exposure to known vulnerabilities. The vulnerability demonstrates the importance of proper input validation and memory management in multimedia processing applications, highlighting the need for robust error handling in third-party libraries that form the foundation of many consumer applications.