CVE-2026-78514 in Office
Summary
by MITRE • 09/09/2026
Use after free in Microsoft Office Word allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described involves a use-after-free error within the Microsoft Office Word application, specifically affecting components that process documents received or accessed over a network. This class of memory corruption vulnerabilities arises when software continues to reference a pointer after the memory it points to has been deallocated and potentially reused for other purposes. In the context of Microsoft Word, this flaw typically manifests during the parsing and rendering of complex document structures, such as those containing embedded objects, macros, or specific formatting elements that trigger internal memory management routines. When an attacker crafts a malicious document designed to exploit this condition, they can manipulate the timing of memory allocation and deallocation to cause the application to write data into freed memory regions or execute code located in those reclaimed spaces.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow for arbitrary read and write operations within the process space of the vulnerable application. By carefully controlling what is allocated in the freed memory slot before it is accessed again, an attacker can achieve precise control over program execution flow. This often leads to remote code execution with the privileges of the currently logged-in user. Since Microsoft Office applications are widely used for business and personal communication, they represent a high-value target for attackers seeking initial access to corporate networks or individual systems. The ability to execute code remotely means that an attacker does not need physical access or local account credentials on the victim machine; instead, delivery can be achieved through phishing emails containing malicious attachments or by hosting the exploit on compromised websites accessed via drive-by downloads.
The operational impact of this vulnerability is severe, as it compromises the confidentiality, integrity, and availability of affected systems. Successful exploitation allows an unauthorized attacker to install programs, view, change, or delete data, and create new accounts with full user rights. In enterprise environments, this can serve as a foothold for lateral movement, where attackers pivot from compromised endpoints to more critical servers and databases. The risk is exacerbated by the fact that Microsoft Office documents are frequently exchanged across organizational boundaries, making it difficult to predict which users might encounter malicious files. Furthermore, because these vulnerabilities often exist in widely deployed software components, they can be weaponized quickly for widespread campaigns targeting multiple organizations simultaneously.
Mitigation strategies must focus on both technical controls and user awareness. Organizations should ensure that all Microsoft Office products are updated with the latest security patches released by Microsoft to address known memory corruption flaws. Implementing application control policies or whitelisting solutions can prevent untrusted scripts from executing within Office applications, thereby reducing the attack surface even if a vulnerability is present. Additionally, deploying advanced email filtering and endpoint detection and response (EDR) systems can help identify and block malicious documents before they reach end-user devices. User training remains critical; employees should be educated to recognize suspicious attachments and avoid opening files from untrusted sources. From an architectural standpoint, enabling features like Protected View for documents received from the internet adds a layer of isolation that limits the potential damage if exploitation occurs.
This vulnerability aligns with CWE-416, which defines use after free as referencing memory after it has been freed, leading to unpredictable behavior and potential security breaches. In terms of offensive cyber operations taxonomy, this exploit technique corresponds to MITRE ATT&CK techniques related to initial access via spearphishing attachment or drive-by compromise, followed by execution through command and script interpreter mechanisms within the context of a trusted application like Microsoft Word. Understanding these mappings helps security teams prioritize defenses against common attack vectors that leverage memory corruption flaws in productivity software. Continuous monitoring for anomalous process behavior, such as Office applications spawning unexpected child processes or accessing sensitive system directories, can also aid in detecting exploitation attempts in real-time.