CVE-2026-68816 in Excel
Summary
by MITRE • 08/12/2026
Stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 08/12/2026
A stack-based buffer overflow vulnerability exists within Microsoft Office Excel that enables remote code execution by unauthorized attackers who can manipulate the application's memory handling mechanisms. This flaw occurs when Excel processes malformed data structures in spreadsheet files, specifically during operations involving complex data types or formulas that exceed allocated stack buffer boundaries. The vulnerability stems from insufficient input validation and improper bounds checking within Excel's parsing routines for various file formats including xls, xlsx, and xlsm. When an attacker crafts malicious spreadsheet content that triggers the overflow condition, the application's stack memory becomes corrupted, potentially allowing arbitrary code execution with the privileges of the currently logged-in user.
The technical implementation of this vulnerability involves the exploitation of memory corruption patterns that occur during Excel's internal processing of structured data elements. Attackers typically craft specially formatted spreadsheet files containing oversized arrays or recursive data structures that cause the application to write beyond allocated stack space. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, where insufficient bounds checking allows data to overwrite adjacent memory locations including return addresses and function pointers. The attack vector commonly involves social engineering techniques where users open malicious files through email attachments or web downloads, making this a prevalent target for phishing campaigns and drive-by download attacks.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with persistent access to affected systems. Once successfully exploited, the malicious code can establish backdoors, exfiltrate sensitive data, or deploy additional malware payloads within the victim's environment. The vulnerability affects multiple versions of Microsoft Office including Excel 2016, 2019, and Office 365, creating widespread exposure across enterprise networks where spreadsheet processing is common. Organizations running unpatched systems face significant risk of lateral movement through the network as attackers can use compromised Excel instances to gain access to other connected systems. The vulnerability also aligns with ATT&CK technique T1059.005 for command and scripting interpreter usage, particularly when attackers leverage the compromised environment to execute additional malicious commands.
Mitigation strategies should prioritize immediate patch deployment through Microsoft's regular security updates and monthly bulletins. Organizations must implement layered security approaches including email filtering solutions that scan for suspicious spreadsheet attachments, network segmentation to limit lateral movement, and user awareness training to prevent social engineering attacks. Application whitelisting policies can restrict execution of unauthorized Office applications, while endpoint detection and response systems should monitor for anomalous Excel process behavior indicating potential exploitation attempts. Regular vulnerability assessments and penetration testing help identify systems that may still be exposed despite patching efforts, ensuring comprehensive coverage across all endpoints that handle spreadsheet processing operations.