CVE-2017-8508 in Outlook
Summary
by MITRE
A security feature bypass vulnerability exists in Microsoft Office software when it improperly handles the parsing of file formats, aka "Microsoft Office Security Feature Bypass Vulnerability".
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Analysis
by VulDB Data Team • 10/17/2019
The vulnerability identified as CVE-2017-8508 represents a critical security feature bypass in Microsoft Office software that stems from improper handling of file format parsing operations. This weakness allows attackers to circumvent intended security protections that are normally enforced during document processing. The flaw specifically manifests when Office applications parse certain file formats, particularly those that contain malformed or specially crafted elements that exploit parsing inconsistencies within the software's internal mechanisms. Such vulnerabilities are particularly dangerous because they can be exploited without user interaction when documents are opened, making them ideal for phishing campaigns and targeted attacks. The security feature bypass occurs at the application layer where Microsoft Office fails to properly validate or sanitize input data during the parsing phase, effectively allowing malicious content to bypass standard security checks that would normally prevent execution of harmful code. This vulnerability directly impacts the integrity of Microsoft Office's security model and undermines the trust model that users place in document processing applications.
The technical implementation of this vulnerability involves the exploitation of parsing inconsistencies within Microsoft Office's file format handlers, particularly affecting applications such as Word, Excel, and PowerPoint. When these applications encounter specially crafted documents containing malformed elements, the parsing logic fails to properly validate the structure and content, allowing attackers to inject malicious code or bypass security controls that should prevent execution of potentially harmful operations. The flaw operates at the level of file format interpretation where the software's parser does not adequately distinguish between legitimate and malicious content during the document parsing process. This allows attackers to craft documents that appear normal to users while containing hidden malicious elements that exploit the parsing inconsistency. The vulnerability is classified under CWE-1233 which specifically addresses improper handling of file format parsing operations and falls within the broader category of software security bypass vulnerabilities. From an attack perspective, this vulnerability enables adversaries to execute code or access sensitive information without triggering the normal security warnings that users would expect when opening documents.
The operational impact of CVE-2017-8508 extends beyond simple document processing failures and represents a significant threat to enterprise security environments where Microsoft Office is extensively used. When exploited, this vulnerability can enable attackers to execute arbitrary code on affected systems, potentially leading to full system compromise and lateral movement within networks. The vulnerability's ability to bypass security features makes it particularly dangerous in targeted attacks where adversaries seek to avoid detection while maintaining persistence. Organizations that rely on Microsoft Office for daily operations face substantial risk when this vulnerability exists, as it can be exploited through various attack vectors including email attachments, web downloads, and removable media. The vulnerability's exploitation does not require user interaction beyond opening the malicious document, making it particularly effective for social engineering campaigns. Security teams must consider this vulnerability as a critical threat that can undermine the security posture of entire organizations, particularly when combined with other exploitation techniques that may leverage the same underlying parsing inconsistencies.
Mitigation strategies for CVE-2017-8508 should encompass both immediate patch management and operational security measures. Microsoft released security updates that address the parsing inconsistencies in Office applications, and organizations must prioritize deployment of these patches across all affected systems. Additionally, implementing strict document handling policies that limit the opening of documents from untrusted sources provides crucial operational protection. Network-based controls such as email filtering and web content filtering can help prevent delivery of malicious documents to end users. Security monitoring should focus on detecting unusual document opening patterns and potential exploitation attempts within network traffic. Organizations should consider implementing application whitelisting to restrict execution of Office applications from untrusted locations and employ sandboxing techniques for document processing. The vulnerability's classification under ATT&CK technique T1204.002 emphasizes the need for comprehensive endpoint protection measures that can detect and prevent exploitation attempts. Regular security awareness training for users helps reduce the risk of successful exploitation through social engineering approaches that rely on users opening malicious documents. Organizations should also implement regular vulnerability assessments to identify and remediate similar parsing inconsistencies that may exist in other software applications.