CVE-2015-2558 in Excel
Summary
by MITRE
Use-after-free vulnerability in Microsoft Excel 2007 SP3, Excel 2010 SP2, Excel 2013 SP1, Excel 2013 RT SP1, Excel 2016, Excel for Mac 2011, Excel 2016 for Mac, Excel Viewer, Office Compatibility Pack SP3, and Excel Services on SharePoint Server 2007 SP3, 2010 SP2, and 2013 SP1 allows remote attackers to execute arbitrary code via a long fileVersion element in an Office document, aka "Microsoft Office Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 06/20/2022
The CVE-2015-2558 vulnerability represents a critical use-after-free flaw in Microsoft Excel products across multiple versions and platforms, including Excel 2007 SP3, Excel 2010 SP2, Excel 2013 SP1, Excel 2013 RT SP1, Excel 2016, Excel for Mac 2011, Excel 2016 for Mac, Excel Viewer, Office Compatibility Pack SP3, and Excel Services on SharePoint Server 2007 SP3, 2010 SP2, and 2013 SP1. This vulnerability falls under the CWE-416 category of Use After Free, which occurs when a program continues to reference memory after it has been freed, creating opportunities for attackers to manipulate memory contents. The flaw specifically manifests when processing a long fileVersion element within Office documents, presenting a significant security risk that can be exploited remotely.
The technical implementation of this vulnerability involves the improper handling of memory allocation and deallocation during the parsing of Office document structures. When Excel encounters a malformed fileVersion element that exceeds expected boundaries, the application fails to properly validate the input data before attempting to access memory that has already been released. This memory corruption occurs in the context of document parsing and rendering, where the application's memory management routines do not adequately protect against malicious input sequences. The vulnerability is particularly dangerous because it can be triggered through legitimate Office document processing, making it difficult to distinguish between benign and malicious content.
From an operational perspective, this vulnerability enables remote code execution attacks that can compromise systems running affected Excel versions. Attackers can craft malicious Office documents containing the specially crafted long fileVersion element that triggers the use-after-free condition when the document is opened or even when it is simply loaded into memory. The attack vector is particularly concerning because it can be delivered through email attachments, web downloads, or SharePoint documents, making it accessible to attackers without requiring local system access. The exploitability of this vulnerability is enhanced by the fact that it affects multiple platforms and versions, increasing the potential attack surface significantly. This vulnerability aligns with ATT&CK technique T1203 by leveraging application weaknesses to execute arbitrary code, and it represents a classic example of how memory safety issues in productivity software can create persistent security risks.
The impact of CVE-2015-2558 extends beyond individual system compromise to affect enterprise environments where Office documents are frequently shared and processed. Organizations using affected Excel versions face significant risks including data breaches, system infiltration, and potential lateral movement within networks where attackers could establish persistent access. The vulnerability's presence in Excel Services on SharePoint Server further amplifies the risk, as it could allow attackers to compromise entire document management systems. Security professionals must recognize that this vulnerability demonstrates the ongoing challenges in memory safety within complex office productivity applications and underscores the importance of timely patch management and application hardening measures. Organizations should implement layered defenses including email filtering, document validation, and regular security updates to mitigate the risk of exploitation. The vulnerability also highlights the necessity of following secure coding practices such as those recommended in the CERT/CC Secure Coding Standards, which emphasize proper memory management and input validation to prevent use-after-free conditions.