CVE-2026-97743 in Office
Summary
by MITRE • 10/15/2026
Use after free in Microsoft Office Excel allows an unauthorized attacker to disclose information 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, specifically affecting how memory management operations are handled during document processing or rendering tasks. In software development, a use-after-free condition occurs when a program continues to use a pointer after the memory it points to has been freed and potentially reallocated for other purposes. This flaw typically arises from improper lifecycle management of objects in memory, where references to deallocated memory blocks are not properly nullified or checked before subsequent access attempts. When an attacker crafts a malicious Excel file containing specific data structures that trigger this sequence, the application may read from or write to invalid memory locations, leading to unpredictable behavior and potential exploitation.
From a technical perspective, this flaw allows for information disclosure over a network because the corrupted state of the application can be manipulated to leak sensitive data stored in adjacent memory regions. By carefully controlling the contents of the malicious file, an attacker can influence how Excel processes specific elements such as formulas, embedded objects, or complex formatting rules. The resulting out-of-bounds read operation exposes internal application states, user credentials, clipboard content, or other confidential information that was previously loaded into the process address space. This capability transforms a standard memory corruption bug into a remote data exfiltration vector, enabling unauthorized access to critical system resources without requiring direct execution privileges on the target machine beyond opening the file in Excel.
The operational impact of this vulnerability is significant for organizations relying on Microsoft Office products for daily operations. Since Excel files are commonly exchanged via email and network shares, an attacker can distribute malicious documents through social engineering tactics such as phishing campaigns. Once a victim opens the crafted document, the use-after-free condition triggers automatically during rendering or calculation phases, allowing the attacker to silently extract sensitive information from the user's environment. This could include corporate secrets, personal identifiable information, authentication tokens, or configuration details that facilitate further attacks within the network perimeter. The ability to disclose this data remotely makes it particularly dangerous as it does not require physical access or elevated system privileges on the target host beyond standard user-level execution rights for Office applications.
To mitigate risks associated with this vulnerability, organizations should ensure that all Microsoft Office installations are updated with the latest security patches released by Microsoft. These updates typically include fixes to memory management routines and enhanced validation checks before accessing freed memory blocks. Additionally, implementing application control policies can restrict the execution of untrusted scripts or macros within Excel files, reducing the attack surface for exploitation. Users should be trained to recognize suspicious attachments and avoid opening documents from unknown sources. Network-level monitoring tools can also detect anomalous outbound data transfers that may indicate successful exfiltration attempts following such an exploit.
This vulnerability aligns with Common Weakness Enumeration (CWE) identifier CWE-416, which defines use-after-free conditions as a critical class of memory safety errors. In the context of the MITRE ATT&CK framework, this exploitation technique falls under Tactic TA0005 for Defense Evasion and specifically relates to techniques involving resource hijacking or data staging through local system compromise via application vulnerabilities. The remote nature of the attack vector places it within the Initial Access phase when considering how attackers gain footholds in enterprise environments by leveraging trusted applications like Microsoft Office. Addressing this issue requires a combination of timely patch management, user awareness training, and robust endpoint protection strategies to prevent exploitation and limit potential data loss outcomes.