CVE-2026-65661 in Office
Summary
by MITRE • 08/11/2026
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 08/12/2026
A heap-based buffer overflow vulnerability exists within Microsoft Office applications that enables remote code execution by malicious actors who can manipulate vulnerable software components through crafted Office documents or files. This critical security flaw resides in the memory management handling of Office's document processing engines, specifically affecting how the application allocates and manages heap memory when parsing certain file formats such as word processing documents, spreadsheets, or presentation files. The vulnerability stems from insufficient bounds checking mechanisms that fail to validate the size of data being copied into allocated heap buffers, allowing attackers to overwrite adjacent memory locations with malicious code payloads. When a user opens a maliciously crafted Office document, the application's parsing routine executes without proper input validation, leading to buffer overflow conditions that can be exploited to redirect program execution flow and ultimately achieve arbitrary code execution within the context of the affected user's privileges. The attack typically requires social engineering to convince users to open compromised documents, making this vulnerability particularly dangerous in enterprise environments where users frequently interact with external email attachments or shared files.
The technical implementation of this heap-based buffer overflow aligns with common software security weaknesses categorized under CWE-121 Heap-based Buffer Overflow, which specifically addresses situations where insufficient bounds checking allows attackers to write beyond allocated memory boundaries. The vulnerability operates within the application's memory management subsystem and can be leveraged through techniques such as stack pivoting or return-oriented programming to bypass modern exploit mitigation mechanisms like data execution prevention and address space layout randomization. According to the MITRE ATT&CK framework, this vulnerability maps to the technique T1203 Exploitation for Client Execution, where adversaries leverage software vulnerabilities to execute malicious code on targeted systems. The exploitation process typically involves crafting a specially formatted Office document that triggers the vulnerable parsing code path when opened by an affected Microsoft Office version, causing memory corruption that allows attackers to inject and execute their payload.
The operational impact of this vulnerability extends beyond simple local privilege escalation as it represents a significant threat vector for initial access and lateral movement within corporate networks. Attackers can utilize this vulnerability to establish persistent presence on compromised systems through the execution of malicious binaries or scripts that maintain access even after system reboots. The vulnerability affects multiple Microsoft Office applications including Word, Excel, PowerPoint, and Access across various Windows operating system versions, making it particularly attractive to threat actors seeking broad exploitation capabilities. Organizations risk data breaches, system compromise, and potential lateral movement throughout their networks when this vulnerability remains unpatched, as successful exploitation can lead to complete system control and access to sensitive corporate information. The exploitability of this vulnerability is enhanced by the widespread use of Microsoft Office across enterprise environments, creating a large attack surface that threat actors actively target.
Mitigation strategies for this heap-based buffer overflow vulnerability require immediate implementation of security patches provided by Microsoft through regular security updates and the deployment of additional protective measures. Organizations should prioritize patch management programs that ensure all Windows systems receive timely security updates, particularly focusing on the specific Office application versions affected by the vulnerability. Network segmentation and email filtering solutions can help reduce attack surface by blocking suspicious Office document attachments from external sources, while endpoint protection solutions should be configured to monitor for suspicious file execution patterns and memory corruption indicators. Security awareness training programs should emphasize the importance of verifying document sources and avoiding opening unexpected email attachments that may contain malicious Office files designed to exploit this vulnerability. Additionally, system administrators should implement application whitelisting policies that restrict execution of Office applications from untrusted network locations and maintain regular security assessments to identify potentially vulnerable systems that have not yet received necessary patches. The implementation of memory protection features such as heap randomization and stack canaries can provide additional defense-in-depth measures against exploitation attempts targeting this specific class of buffer overflow vulnerabilities.