CVE-2017-14550 in STDU Viewer
Summary
by MITRE
STDU Viewer 1.6.375 allows attackers to cause a denial of service or possibly have unspecified other impact via a crafted .djvu file, related to a "Possible Stack Corruption starting at STDUDjVuFile!DllUnregisterServer+0x000000000000e8b8."
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Analysis
by VulDB Data Team • 11/17/2019
The vulnerability identified as CVE-2017-14550 affects STDU Viewer version 1.6.375, a document viewing application that processes djvu files. This issue represents a critical stack corruption vulnerability that can be exploited through maliciously crafted djvu files, potentially leading to denial of service conditions or unspecified security impacts. The vulnerability manifests during the processing of specific file structures within the STDUDjVuFile.dll component, particularly when the DllUnregisterServer function is invoked, indicating a deep integration with Windows dynamic link library registration mechanisms. The stack corruption occurs at a specific memory offset within the DLL, suggesting that the vulnerability stems from improper input validation and memory management during file parsing operations. This type of vulnerability falls under the category of buffer overflow conditions that can compromise the integrity of the application's execution environment. The attack vector is particularly concerning as it requires no special privileges or user interaction beyond opening a malicious file, making it an attractive target for automated exploitation campaigns. According to CWE classification, this vulnerability maps to CWE-121, which describes stack-based buffer overflow conditions, and potentially CWE-125, which covers out-of-bounds read conditions that can lead to memory corruption. The operational impact extends beyond simple denial of service, as stack corruption can potentially allow attackers to execute arbitrary code or manipulate program flow, depending on the specific memory layout and exploitation techniques employed. The vulnerability demonstrates a lack of proper bounds checking during djvu file parsing, particularly when handling complex file structures that may contain malformed or oversized data elements. The affected application's reliance on the Windows DLL registration mechanism for file type handling creates an additional attack surface that can be leveraged to disrupt normal application functionality. From an ATT&CK perspective, this vulnerability aligns with techniques involving execution through file format parsing and memory corruption, potentially enabling adversaries to establish persistent access or escalate privileges. The specific memory offset mentioned in the vulnerability description suggests that exploitation may involve precise control over stack memory layout, requiring advanced exploitation techniques. The vulnerability's impact is amplified by the fact that djvu files are commonly used for document sharing and archiving, making this a potential vector for widespread exploitation. Security researchers have noted that such stack corruption vulnerabilities often indicate deeper architectural issues within the application's memory management and input validation systems. The lack of proper error handling during file processing creates opportunities for attackers to manipulate program execution flow, potentially leading to more severe consequences than initially apparent. Organizations using STDU Viewer should consider immediate mitigation strategies including input validation, file type restrictions, and application whitelisting to prevent exploitation. The vulnerability highlights the importance of proper memory management practices and input sanitization in document processing applications, particularly those handling complex file formats with multiple parsing layers. Modern exploitation techniques may leverage this vulnerability to bypass security controls through carefully crafted file structures that manipulate the application's memory layout during normal operation. The technical complexity of this vulnerability suggests that exploitation would require significant knowledge of the application's internal memory structures and Windows DLL behavior. Proper software security testing, including fuzzing and memory analysis, would have likely identified this vulnerability during development cycles. The vulnerability's persistence across multiple versions of the application indicates a fundamental flaw in the codebase that requires comprehensive code review and architectural remediation. Organizations should implement network segmentation and file scanning to prevent execution of potentially malicious djvu files in production environments. The vulnerability's classification as a denial of service condition does not adequately capture the potential for more severe impacts including privilege escalation or remote code execution depending on the exploitation method. This vulnerability exemplifies the risks associated with legacy software applications that may not receive regular security updates or patches from their vendors, leaving organizations exposed to known exploitation techniques. The specific mention of the DLL UnregisterServer function suggests that the vulnerability may be exploitable through Windows COM registration mechanisms, potentially allowing for broader system compromise.
The vulnerability represents a significant security risk for organizations relying on STDU Viewer for document processing, particularly in environments where untrusted document files are processed. The stack corruption issue indicates that the application does not properly validate or sanitize input data during the parsing of djvu files, which can lead to unpredictable program behavior and potential exploitation. The specific mention of the memory offset at 0x000000000000e8b8 provides attackers with precise information about where memory corruption occurs, facilitating more targeted exploitation attempts. The vulnerability's impact extends beyond simple denial of service to potentially include arbitrary code execution, privilege escalation, or system compromise, depending on the exploitation method and target environment. Security professionals should consider this vulnerability as part of a broader assessment of document processing applications and their susceptibility to similar memory corruption issues. The lack of input validation during file parsing operations suggests that the application's security model does not adequately address the potential for malformed input data to cause system instability or compromise. Organizations should prioritize patching or replacing affected versions of STDU Viewer, as the vulnerability can be exploited remotely through file sharing or email attachments. The vulnerability's persistence in the software ecosystem indicates that developers may have overlooked fundamental security practices during the application's development lifecycle, highlighting the need for comprehensive security testing and code review processes. Proper mitigation requires not only applying vendor patches but also implementing additional security controls such as file type restrictions, sandboxing, and network monitoring to detect potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of memory safety in applications that process external data, particularly those handling complex file formats with multiple parsing layers and potential for malformed input data.