CVE-2015-2555 in Excel
Summary
by MITRE
Use-after-free vulnerability in Microsoft Excel 2010 SP2, Excel 2013 SP1, Excel 2013 RT SP1, Excel 2016, Excel for Mac 2011, Excel 2016 for Mac, and Excel Services on SharePoint Server 2010 SP2 and 2013 SP1 allows remote attackers to execute arbitrary code via a crafted calculatedColumnFormula object in an Office document, aka "Microsoft Office Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 06/20/2022
This vulnerability represents a critical use-after-free flaw in Microsoft Excel's handling of calculated column formulas within Office documents. The vulnerability exists in multiple versions of Excel including 2010 SP2, 2013 SP1, 2013 RT SP1, 2016, and various Mac versions, as well as Excel Services on SharePoint Server 2010 SP2 and 2013 SP1. The flaw manifests when Excel processes a specially crafted calculatedColumnFormula object, which triggers memory corruption that can be exploited by remote attackers to execute arbitrary code on vulnerable systems.
The technical mechanism behind this vulnerability involves improper memory management during the processing of calculated column formulas in Excel documents. When a maliciously crafted document containing a specially constructed calculatedColumnFormula object is opened, the application fails to properly validate memory references, leading to a situation where freed memory locations are accessed after they have been reallocated. This use-after-free condition creates a predictable memory corruption scenario that can be leveraged by attackers to inject and execute malicious code with the privileges of the affected user. The vulnerability falls under CWE-416, which specifically addresses the use of freed memory, and represents a classic memory safety issue that has plagued software applications for decades.
The operational impact of this vulnerability is severe, as it enables remote code execution without requiring user interaction beyond opening a malicious document. Attackers can craft Office documents that, when opened by victims, automatically trigger the memory corruption and execute malicious payloads. This makes the vulnerability particularly dangerous in enterprise environments where users frequently open documents from external sources or email attachments. The vulnerability's presence in Excel Services on SharePoint Server 2010 and 2013 further expands its attack surface to web-based Office document processing environments, potentially allowing attackers to compromise entire SharePoint infrastructures. According to ATT&CK framework, this vulnerability maps to T1059.005 (Command and Scripting Interpreter: Visual Basic) and T1203 (Exploitation for Client Execution) categories, demonstrating how attackers can leverage document-based exploitation techniques to gain system access.
Mitigation strategies for this vulnerability require immediate patch application from Microsoft as the primary defense mechanism, since the flaw exists at the core memory management level of affected Excel versions. Organizations should implement strict document validation policies, particularly for documents received from external sources, and consider deploying email filtering solutions that can identify and block potentially malicious Office documents. Network segmentation and privileged access controls should be implemented to limit the potential impact if exploitation occurs. Additionally, users should be trained to avoid opening suspicious documents and to verify document sources before opening attachments. The vulnerability demonstrates the critical importance of maintaining up-to-date software patches and implementing defense-in-depth strategies that protect against memory corruption exploits through multiple control layers including application whitelisting, sandboxing, and regular security assessments to identify and remediate similar vulnerabilities in the application ecosystem.