CVE-2018-6217 in WPS Office
Summary
by MITRE
The WStr::_alloc_iostr_data() function in kso.dll in Kingsoft WPS Office 10.1.0.7106 and 10.2.0.5978 allows remote attackers to cause a denial of service (application crash) via a crafted (a) web page, (b) office document, or (c) .rtf file.
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Analysis
by VulDB Data Team • 12/27/2019
The vulnerability identified as CVE-2018-6217 resides within the WStr::_alloc_iostr_data() function in the kso.dll component of Kingsoft WPS Office versions 10.1.0.7106 and 10.2.0.5978. This flaw represents a classic buffer overflow condition that manifests when the application processes specially crafted input data through various file formats including web pages, office documents, and .rtf files. The vulnerability operates at the application layer where improper memory management leads to application instability and potential system compromise. The affected software component handles string allocation operations for input/output data streams, making it susceptible to malformed input that exceeds allocated buffer boundaries.
The technical exploitation of this vulnerability occurs when WPS Office attempts to process maliciously constructed input data that triggers the _alloc_iostr_data() function to allocate insufficient memory space for the intended string operations. This memory allocation failure results in heap corruption that ultimately causes the application to crash and terminate unexpectedly. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though the actual manifestation occurs in heap memory management. The flaw demonstrates characteristics consistent with memory safety issues where the application fails to properly validate input size limits before allocating memory resources, creating a condition where attacker-controlled data can overwrite adjacent memory regions.
Operationally, this vulnerability presents a significant denial of service risk to users who may inadvertently open maliciously crafted files or visit compromised web pages. The remote attack vector allows adversaries to execute code execution through application crashes without requiring local system access, making it particularly dangerous in enterprise environments where users frequently open documents from external sources. The impact extends beyond simple application instability as the crash can potentially be leveraged for more sophisticated attacks if combined with other vulnerabilities present in the application stack. The vulnerability affects multiple document formats including rtf files, office documents, and web content, expanding the attack surface and increasing the probability of successful exploitation.
Mitigation strategies for CVE-2018-6217 should focus on immediate software updates from Kingsoft to address the memory allocation flaw in kso.dll. Organizations should implement strict file validation policies that restrict the opening of untrusted documents and enforce sandboxing mechanisms when processing external content. Network-based defenses including web application firewalls and content filtering systems can help prevent access to malicious web pages that may trigger the vulnerability. The ATT&CK framework categorizes this vulnerability under T1203 as Exploitation for Execution, where attackers leverage application flaws to achieve system compromise. Security teams should also consider implementing endpoint detection and response solutions to monitor for abnormal application behavior patterns that may indicate exploitation attempts. Regular vulnerability assessments and penetration testing should include evaluation of document processing components to identify similar memory safety issues that could lead to more severe security incidents.