CVE-2017-8631 in Excel
Summary
by MITRE
A remote code execution vulnerability exists in Excel Services, Microsoft Excel 2007 Service Pack 3, Microsoft Excel 2010 Service Pack 2, Microsoft Excel 2013 Service Pack 1, Microsoft Excel 2013 RT Service Pack 1, Microsoft Excel 2016, Microsoft Office Web Apps 2013, Microsoft Office Compatibility Pack Service Pack 3, Microsoft Excel Web App 2013 Service Pack 1, Microsoft Excel Viewer 2007 Service Pack 3, and Office Online Server when they fail to properly handle objects in memory, aka "Microsoft Office Memory Corruption Vulnerability". This CVE ID is unique from CVE-2017-8630, CVE-2017-8632, and CVE-2017-8744.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 01/11/2021
The vulnerability described in CVE-2017-8631 represents a critical memory corruption flaw within Microsoft Office applications, specifically affecting Excel Services and various Excel versions across different platforms. This vulnerability resides in the way these applications handle objects in memory during processing of specific file formats, creating a potential pathway for remote code execution attacks. The flaw manifests when the affected software fails to properly validate or manage memory objects, leading to unpredictable behavior that adversaries can exploit to gain unauthorized system access.
This memory corruption vulnerability operates at the core of Microsoft Office's processing engine, where improper handling of objects in memory creates opportunities for attackers to manipulate the application's execution flow. The technical nature of the flaw suggests that when Excel services process certain malformed or specially crafted spreadsheet files, the memory management routines fail to properly sanitize input data, allowing attackers to inject malicious code that executes with the privileges of the targeted user. The vulnerability's classification as a memory corruption issue aligns with common attack patterns found in the cyber threat landscape and corresponds to CWE-125, which specifically addresses out-of-bounds read conditions in memory management.
The operational impact of CVE-2017-8631 extends beyond simple remote code execution, as it provides attackers with the ability to establish persistent access to compromised systems through Excel Services. Organizations running affected versions of Microsoft Office are particularly vulnerable when they host or process Excel files from untrusted sources, as the attack can occur during normal file handling operations without requiring user interaction beyond opening the malicious file. This makes the vulnerability particularly dangerous in enterprise environments where Excel files are frequently shared and processed through web-based applications, as the attack surface expands to include Office Online Server deployments and web-based Excel applications.
Mitigation strategies for this vulnerability should focus on immediate patching of all affected Microsoft Office versions, along with implementing network-level protections such as firewall rules that restrict access to Excel Services and related web applications. Organizations should also consider deploying application whitelisting solutions to prevent execution of unauthorized binaries and implement strict file validation processes for Excel files received from external sources. The ATT&CK framework categorizes this type of vulnerability exploitation under the T1059 technique for command and script interpreter, while the vulnerability itself relates to T1190 for exploit public-facing application, making comprehensive defensive measures essential for protecting against potential exploitation attempts.