CVE-2017-11878 in Excel
Summary
by MITRE
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 Compatibility Pack Service Pack 3, and Microsoft Excel Viewer 2007 Service Pack 3 allow an attacker to run arbitrary code in the context of the current user by failing to properly handle objects in memory, aka "Microsoft Excel Memory Corruption Vulnerability".
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Analysis
by VulDB Data Team • 01/23/2021
The Microsoft Excel Memory Corruption Vulnerability CVE-2017-11878 represents a critical heap-based buffer overflow flaw that affects multiple versions of Microsoft Excel and related Office components. This vulnerability stems from improper handling of objects in memory during the processing of maliciously crafted Excel files, creating a dangerous attack surface that can be exploited by adversaries to execute arbitrary code with the privileges of the currently logged-in user. The flaw exists within the memory management mechanisms of Excel's parsing engine, specifically when processing certain file formats that contain malformed data structures. Security researchers have classified this issue as a heap-based buffer overflow under CWE-122, which falls under the broader category of memory corruption vulnerabilities that have been consistently exploited in various attack scenarios throughout the cybersecurity landscape.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious Excel file that triggers improper memory handling during the parsing process. When a user opens such a file, the vulnerable Excel component attempts to process malformed objects in memory without adequate bounds checking or validation. This leads to a situation where attacker-controlled data can overwrite adjacent memory locations, potentially allowing code execution in the context of the current user. The vulnerability is particularly concerning because it does not require user interaction beyond opening the malicious file, making it susceptible to drive-by download attacks and social engineering campaigns. The memory corruption occurs during the processing of structured data within Excel's internal memory management system, creating a pathway for attackers to manipulate execution flow and inject malicious payloads.
The operational impact of CVE-2017-11878 extends beyond simple code execution, as it provides attackers with a persistent foothold within targeted environments. This vulnerability has been actively exploited in the wild, particularly through spear-phishing campaigns where attackers embed malicious Excel files in email attachments. Once successfully exploited, the vulnerability allows attackers to establish a foothold for further lateral movement within networks, potentially leading to full system compromise. The attack vector aligns with techniques described in the MITRE ATT&CK framework under the T1059.005 sub-technique for command and scripting interpreter, as attackers can leverage the executed code to establish persistence mechanisms. Organizations running affected versions of Excel are particularly vulnerable because the attack requires no specialized knowledge or privileged access beyond the ability to deliver a malicious file to a target user.
Mitigation strategies for this vulnerability should include immediate deployment of Microsoft security patches and updates, as the vendor released comprehensive fixes for all affected versions of Excel. System administrators should implement strict email filtering and sandboxing mechanisms to prevent users from opening potentially malicious Excel files. The principle of least privilege should be enforced, ensuring that users operate with minimal necessary permissions to reduce the impact of successful exploitation. Network segmentation and endpoint protection solutions can provide additional layers of defense by monitoring for suspicious file execution patterns and anomalous memory access behaviors. Organizations should also conduct regular security awareness training to educate users about recognizing phishing attempts and the dangers of opening unexpected Excel files. From a compliance standpoint, this vulnerability highlights the importance of maintaining up-to-date software inventory and implementing robust patch management processes to prevent similar issues from occurring in the future.