CVE-2026-78524 in Office
Summary
by MITRE • 09/09/2026
Out-of-bounds write in Microsoft Office 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 represents a critical security flaw within the Microsoft Office suite, specifically categorized as an out-of-bounds write error. This type of memory corruption issue arises when software writes data beyond the boundaries of allocated memory buffers, potentially overwriting adjacent memory locations that may contain executable code or control structures such as return addresses and function pointers. In the context of network-based attacks, this flaw is particularly dangerous because it can be triggered remotely without requiring any user interaction beyond opening a maliciously crafted document or file hosted on an attacker-controlled server. The exploitation mechanism typically involves crafting specific input data that exploits parsing logic errors within Office components like Word, Excel, or PowerPoint, allowing the attacker to gain arbitrary code execution privileges on the victim's system with the same rights as the current user.
From a technical perspective, out-of-bounds writes are classified under CWE-787 in the Common Weakness Enumeration standard, which denotes access to a memory location outside of an allocated buffer. This weakness often leads to undefined behavior and can be leveraged for privilege escalation or remote code execution depending on how the overwritten memory is utilized by the operating system's security mechanisms such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR). Attackers may employ advanced techniques like heap spraying or use-of-after-free scenarios in conjunction with this vulnerability to bypass these mitigations. The attack vector aligns with ATT&CK technique T1203, which covers exploitation for client execution, where the adversary relies on user interaction to trigger the payload through social engineering tactics such as phishing emails containing malicious attachments that exploit this specific memory corruption flaw.
The operational impact of successfully exploiting this vulnerability is severe, resulting in full compromise of the affected system. An unauthorized attacker can execute arbitrary code within the context of the logged-in user, potentially leading to data theft, installation of malware, creation of backdoors, or lateral movement across a network if the compromised machine serves as an entry point for further attacks. Since Microsoft Office is ubiquitous in enterprise environments, this vulnerability poses a significant risk to organizational security postures, especially when users are accustomed to opening documents from external sources without rigorous verification. The ability to execute code over the network means that physical access or local account compromise by the attacker is not required, making it a high-severity threat suitable for targeted campaigns and widespread automated attacks.
To mitigate this risk, organizations must ensure that all Microsoft Office applications are updated with the latest security patches released by Microsoft addressing this specific out-of-bounds write issue. Administrators should implement application control policies to restrict the execution of untrusted scripts or macros within Office documents unless explicitly approved. Additionally, deploying endpoint detection and response solutions can help identify anomalous behavior associated with exploitation attempts, such as unusual memory access patterns or process injections originating from Office processes. Users should be educated on recognizing phishing indicators and avoiding opening attachments from unknown senders. Network segmentation and strict firewall rules limiting inbound connections to file servers hosting untrusted content can also reduce the attack surface by preventing direct exposure of vulnerable services to external networks.