CVE-2026-97759 in Office
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 involves a use-after-free error within the Microsoft Office Excel application, which presents a critical security risk by allowing remote attackers to achieve arbitrary code execution through network-based attacks. This class of memory corruption flaw occurs when software continues to use a pointer after it has been freed from dynamic memory allocation. In the context of Excel, this typically manifests when processing specially crafted files or data streams that trigger the application to release a memory block but subsequently attempt to access or manipulate that same block through dangling pointers. The operational impact is severe because successful exploitation can lead to full system compromise on affected machines without requiring user interaction beyond opening the malicious file or visiting a compromised website hosting exploit code, thereby facilitating widespread lateral movement in enterprise environments where Excel documents are routinely exchanged over networks.
From a technical perspective, use-after-free vulnerabilities stem from improper management of object lifecycles within the application's memory space. When an attacker crafts input that forces Excel to free a specific data structure while retaining references to it elsewhere in the code execution path, subsequent operations on those stale references can overwrite adjacent heap metadata or execute arbitrary shellcode placed by the attacker during the allocation phase. This mechanism bypasses many modern exploit mitigations such as Data Execution Prevention and Address Space Layout Randomization if combined with additional techniques like information disclosure for address calculation. The network vector implies that attackers do not need physical access to the target system, making this a high-severity remote code execution flaw that can be propagated via email attachments, shared drives, or web-based document viewers integrated into corporate portals.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-416, which defines use-after-free as a critical memory safety issue prevalent in complex software applications like office suites. Furthermore, the exploitation technique maps to MITRE ATT&CK tactics involving Initial Access and Execution, specifically leveraging techniques such as Spearphishing Attachment or Exploit Public-Facing Application depending on how the malicious content is delivered. The ability to execute code over the network significantly elevates the threat level compared to local-only exploits because it enables automated scanning campaigns targeting vulnerable versions of Excel across organizational boundaries. Defense-in-depth strategies must therefore prioritize both application-level hardening and perimeter security controls to mitigate this risk effectively.
Mitigation efforts should focus on immediate patching by applying the latest cumulative updates released by Microsoft, which address these memory management flaws through rigorous code review and static analysis tools designed to detect dangling pointer usage. Administrators are advised to restrict macro execution policies within Excel settings to prevent additional attack vectors that often accompany use-after-free exploits in document-based attacks. Additionally, deploying endpoint detection and response solutions capable of monitoring for anomalous heap activity or unexpected process creation following file open events can provide early warning indicators of exploitation attempts. Network segmentation should also be considered to limit the blast radius if a workstation is compromised, ensuring that lateral movement via SMB or other network protocols is restricted between critical systems and general user endpoints until patches are fully deployed across all affected assets.