CVE-2026-97017 in Excel
Summary
by MITRE • 10/15/2026
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Excel application, specifically involving a use-after-free error that can be exploited remotely by an unauthenticated attacker. This type of defect arises when software continues to reference memory after it has been freed or deallocated, leading to undefined behavior in the program's execution flow. In the context of network-based attacks, this flaw typically manifests when Excel processes specially crafted documents containing malformed data structures. When the application attempts to access these corrupted elements, it interacts with invalid pointers that may point to arbitrary locations in memory rather than valid object instances. This discrepancy allows an attacker who controls the content of such a document or stream to manipulate how the application handles memory allocation and deallocation cycles.
From a technical perspective, this vulnerability aligns closely with CWE-416, which defines use-after-free errors as conditions where pointers are used after their associated memory has been released. The operational impact is severe because it enables arbitrary code execution on the victim's system without requiring any user interaction beyond opening or viewing the malicious file through a network share or email attachment. An attacker can craft an Excel workbook that triggers this condition during parsing, thereby gaining control over the instruction pointer and subsequently executing shellcode within the context of the logged-on user. This capability effectively bypasses many traditional perimeter defenses since it relies on social engineering tactics combined with technical exploitation rather than brute force or network service vulnerabilities alone.
The attack vector falls under MITRE ATT&CK technique T1203, which covers Exploitation for Client Execution, specifically targeting office applications as a common entry point into corporate networks. By leveraging this flaw, adversaries can establish persistence, escalate privileges if the user has administrative rights, and move laterally across internal systems using compromised credentials or additional exploits deployed via the initial payload. The severity is further amplified by the ubiquity of Microsoft Office in enterprise environments, making it a high-value target for threat actors seeking widespread access to sensitive data infrastructure.
Mitigation strategies must focus on both technical controls and user awareness training. Organizations should ensure that all systems are patched with the latest security updates provided by Microsoft, which address these memory management issues within Excel's parsing engine. Additionally implementing application whitelisting can prevent unauthorized scripts from executing after exploitation occurs. Network segmentation limits lateral movement potential while endpoint detection and response solutions monitor for anomalous processes spawned by office applications. User education remains critical as well since preventing the opening of suspicious files is often more effective than relying solely on technical mitigations post-exploitation. Regular audits of macro settings and disabling unnecessary features like ActiveX controls reduce the attack surface available to potential exploiters targeting this specific vulnerability class.