CVE-2026-81952 in Office
Summary
by MITRE • 09/09/2026
Heap-based buffer overflow 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 constitutes a critical security flaw within the Microsoft Office Word application, specifically manifesting as a heap-based buffer overflow. This type of memory corruption error occurs when a program writes data beyond the allocated boundaries of a buffer located in the heap segment of computer memory. In the context of Microsoft Office Word, this defect is typically triggered by processing specially crafted documents or files that exploit parsing logic errors within the application's rendering engine or document structure handlers. The attacker crafts input data with specific malformed structures designed to cause an integer overflow or miscalculation during buffer allocation, allowing them to write more data than intended into a fixed-size memory block on the heap.
The operational impact of this vulnerability is severe due to its potential for remote code execution over a network. An unauthorized attacker can leverage this flaw by sending a maliciously constructed document via email or hosting it on a website that the victim visits using Word's web viewing capabilities. When the application processes the malformed file, the heap overflow allows the attacker to overwrite adjacent memory structures, such as function pointers or exception handling records. By carefully controlling the content written beyond the buffer boundary, the attacker can redirect program execution flow to inject and execute arbitrary shellcode within the context of the currently logged-on user. This results in a complete compromise of the affected system, granting the adversary full control over the application and potentially the underlying operating system without any authentication or prior interaction from the victim other than opening the file.
From an industry standards perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-120, which classifies buffer copies without checking size limits as a classic memory safety issue. Furthermore, in terms of tactical behavior within the MITRE ATT&CK framework, this exploit mechanism is consistent with techniques involving exploitation for remote code execution and potentially command and control if followed by beaconing activity. The heap-based nature of the overflow distinguishes it from stack overflows, often requiring more sophisticated exploitation techniques such as heap spraying or using specific object manipulation strategies to achieve reliable code execution across different memory layouts and operating system versions.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided security patches that address the underlying parsing logic errors in Microsoft Office Word. Organizations should ensure that all endpoints are updated with the latest cumulative updates from Microsoft, which typically include fixes for such high-severity vulnerabilities. Additionally, implementing application control policies can restrict the execution of untrusted scripts and macros, thereby reducing the attack surface even if an exploit is attempted. Users should be educated to exercise caution when opening documents received from unknown or untrusted sources, particularly those with double extensions like .doc.exe disguised as legitimate files. Network-level defenses such as intrusion detection systems may also help identify attempts to deliver these malicious payloads by analyzing traffic patterns associated with known exploitation kits targeting Office applications.