CVE-2017-14548 in STDU Viewer
Summary
by MITRE
STDU Viewer 1.6.375 allows attackers to execute arbitrary code or cause a denial of service via a crafted .djvu file, related to a "User Mode Write AV starting at STDUDjVuFile!DllUnregisterServer+0x000000000000854d."
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Analysis
by VulDB Data Team • 11/17/2019
The vulnerability identified as CVE-2017-14548 affects STDU Viewer version 1.6.375, a document viewing application that processes djvu files. This weakness represents a critical security flaw that enables remote code execution or denial of service attacks through maliciously crafted djvu file inputs. The vulnerability manifests during the processing of specially constructed djvu files, specifically when the application attempts to handle file registration operations within the STDUDjVuFile.dll component. The technical root cause involves an access violation occurring in user mode at the DllUnregisterServer function within the STDUDjVuFile.dll module, with the exact memory offset 0x000000000000854d indicating where the application crashes or executes unintended code paths.
This vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-125, representing out-of-bounds read errors. The flaw demonstrates characteristics of heap-based memory corruption that can be exploited through improper input validation and handling of file format structures. The attack vector leverages the application's failure to properly validate djvu file headers and embedded data structures, allowing attackers to craft malicious files that trigger memory corruption during normal file processing operations. The specific error location within DllUnregisterServer suggests that the vulnerability may be triggered during file registration or unregistration processes, potentially through improper handling of file metadata or embedded script elements within the djvu format.
From an operational perspective, this vulnerability presents significant risk to organizations relying on STDU Viewer for document processing, as it allows adversaries to execute arbitrary code on target systems with the privileges of the application user. The denial of service component means that even attempting to open a malicious file could crash the application or potentially the entire system, disrupting normal business operations. The vulnerability can be exploited through social engineering campaigns where users unknowingly open malicious djvu files, or through automated exploitation in environments where such files might be processed automatically. The attack surface is particularly concerning given that djvu files are commonly used for document sharing and archiving, making them a likely target for exploitation in enterprise environments.
Mitigation strategies should focus on immediate patching of the affected STDU Viewer application to version 1.6.376 or later, which contains the necessary fixes for the memory corruption issues. Organizations should implement file validation controls that scan djvu files for known malicious patterns or structures before processing, and consider deploying application whitelisting solutions that restrict execution of unauthorized binaries. Network-based mitigations could include filtering djvu files at perimeter defenses, though this approach may be less effective if the vulnerability is exploited through legitimate business processes. The ATT&CK framework categorizes this vulnerability under T1203, which covers Exploitation for Execution, and potentially T1489, which involves Data Destruction, depending on the specific attack implementation. System administrators should also consider implementing monitoring for unusual process behavior or memory access violations that might indicate exploitation attempts, particularly around the affected DLL module and its functions.
Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected versions of STDU Viewer, and implement proper incident response procedures to handle potential exploitation attempts. Regular security updates and patch management processes should be enforced to prevent similar vulnerabilities from remaining unaddressed in other applications. The vulnerability also highlights the importance of proper input validation and memory safety practices in document processing applications, particularly those handling complex file formats with embedded scripting capabilities that could be exploited for code execution.