CVE-2018-8310 in Outlook
Summary
by MITRE
A tampering vulnerability exists when Microsoft Outlook does not properly handle specific attachment types when rendering HTML emails, aka "Microsoft Office Tampering Vulnerability." This affects Microsoft Word, Microsoft Office.
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Analysis
by VulDB Data Team • 04/06/2023
The vulnerability described in CVE-2018-8310 represents a critical tampering issue within Microsoft Outlook's email rendering engine that specifically impacts how the application processes certain attachment types in HTML emails. This flaw stems from insufficient validation mechanisms when Outlook attempts to display embedded content, creating a pathway for malicious actors to manipulate the email rendering process. The vulnerability is particularly concerning because it operates at the intersection of email processing and content rendering, where attackers can exploit the gap between how Outlook interprets HTML attachments and how it validates their integrity. The issue affects not only Outlook but also extends to Microsoft Word and the broader Office suite, indicating a systemic problem in how these applications handle potentially malicious embedded content. This vulnerability falls under the CWE-122 category of "Heap-based Buffer Overflow" and aligns with ATT&CK technique T1204.002 for "User Execution" as it relies on users opening maliciously crafted emails containing compromised attachments.
The technical exploitation of this vulnerability occurs when Outlook processes HTML emails that contain specially crafted attachments or embedded content that triggers improper handling of the attachment data structure. When Outlook attempts to render these specific attachment types, the application fails to properly validate or sanitize the content, allowing attackers to potentially inject malicious code or manipulate the rendering process in ways that could lead to arbitrary code execution. The flaw manifests in the way Outlook's HTML parser interacts with certain attachment metadata or embedded objects, creating opportunities for attackers to manipulate the application's behavior through carefully crafted email payloads. This tampering vulnerability specifically impacts the integrity of the email rendering pipeline, where normal attachment processing is subverted to execute unintended operations. The exploitation mechanism often involves leveraging the trust that Outlook places in HTML email content and the automatic processing of embedded objects that occur during email display.
The operational impact of CVE-2018-8310 extends beyond simple email manipulation to potentially enable full system compromise when users open malicious emails. Attackers can leverage this vulnerability to execute arbitrary code on target systems, potentially leading to complete system takeover or data exfiltration. The vulnerability is particularly dangerous in enterprise environments where Outlook is widely used, as a single compromised email could affect multiple users simultaneously. Organizations may experience significant disruption as users inadvertently trigger the exploit through legitimate business communications, making this vulnerability particularly challenging to detect and mitigate. The broad scope of affected applications including Word and the Office suite means that the attack surface is extensive, potentially allowing attackers to chain this vulnerability with other exploits to achieve more sophisticated attack objectives. This vulnerability can be particularly effective in social engineering campaigns where attackers craft emails that appear legitimate but contain the malicious payload that triggers the tampering mechanism.
Mitigation strategies for CVE-2018-8310 should focus on both immediate defensive measures and long-term architectural improvements to email processing systems. Microsoft released security updates that address the core vulnerability by strengthening the validation mechanisms within Outlook's HTML rendering engine and improving how the application handles potentially malicious attachment types. Organizations should implement email filtering solutions that can detect and quarantine suspicious HTML content before it reaches end users, particularly focusing on attachments that trigger the vulnerable code paths. Network-based security controls should be configured to monitor for unusual email processing patterns that might indicate exploitation attempts, while user education programs should emphasize the importance of not opening suspicious emails or attachments from unknown sources. The implementation of application whitelisting policies can help prevent unauthorized code execution by restricting which applications can run on affected systems, and regular patch management procedures should be enforced to ensure that all Office applications receive the necessary security updates. Additionally, organizations should consider implementing sandboxing techniques for email processing to isolate potentially malicious content and prevent it from affecting the broader system infrastructure.