CVE-2026-69734 in Office
Summary
by MITRE • 09/09/2026
Integer overflow or wraparound in Microsoft Office Word allows an unauthorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described involves a critical integer overflow condition within the parsing logic of Microsoft Office Word, specifically affecting how certain data structures are handled during document processing operations. Integer overflows occur when an arithmetic operation results in a value that exceeds the maximum capacity for a given numeric type, causing it to wrap around to a negative number or a very small positive number rather than throwing an error. In the context of Microsoft Office Word, this flaw typically manifests when parsing complex documents containing specially crafted elements such as embedded objects, specific formatting codes, or malformed metadata fields. An attacker can exploit this weakness by constructing a malicious document that triggers the overflow during the rendering or validation phase. This miscalculation leads to incorrect memory allocation calculations, where the application allocates significantly less memory than required for subsequent operations.
This misallocation creates a buffer over-read condition rather than the more commonly discussed buffer overwrite scenario often associated with integer bugs in this context. When the application attempts to read data into or process buffers based on these miscalculated sizes, it accesses memory regions beyond the intended boundaries of the allocated block. Because the overflow allows for negative indices or excessively large size parameters that wrap around, the software may inadvertently expose contents from adjacent areas of system memory. These adjacent memory locations can contain sensitive information such as stack variables, heap metadata, pointers to other objects, or even credentials and session tokens if they reside in nearby allocations. The disclosure is not limited to local access; because Microsoft Office Word frequently processes documents received via email attachments or downloaded from web sources, an attacker positioned on a network can deliver the malicious payload remotely.
The operational impact of this vulnerability centers on unauthorized information disclosure rather than immediate code execution or system compromise. While buffer overflows are often feared for their potential to lead to remote code execution through stack smashing, in this specific instance, the primary consequence is the leakage of internal application state and potentially sensitive user data into an attacker-controlled context. This could allow a sophisticated adversary to perform further reconnaissance by analyzing leaked memory contents to identify running processes, loaded modules, or active network connections within the victim's environment. Such information can serve as stepping stones for more advanced attacks, including privilege escalation or targeted phishing campaigns based on discovered organizational structures and user roles visible in the disclosed data. The ability to disclose this information over a network significantly lowers the barrier for exploitation, allowing for automated scanning and large-scale targeting without requiring physical access or local account privileges on the victim's machine.
From a classification perspective, this vulnerability aligns with CWE-190 Integer Overflow or Wraparound, which describes errors resulting from arithmetic operations that exceed the maximum value of an integer type. It also relates closely to CWE-125 Out-of-bounds Read, as the overflow facilitates access to memory regions outside the intended buffer limits. In terms of adversary tactics, this exploit technique corresponds to ATT&CK T1005 Data from Local System which covers techniques for accessing data stored locally on a target system without direct interaction with an application interface but rather through exploitation of software flaws that expose internal states. It may also touch upon ATT&CK T1046 Network Service Discovery if the leaked information reveals network configurations or active services, aiding in lateral movement planning within a compromised network segment.
Mitigation strategies for this vulnerability require immediate attention to patch management and defensive configuration practices. Organizations must ensure that all instances of Microsoft Office Word are updated with the latest security patches released by Microsoft addressing this specific integer overflow flaw. Since exploitation relies on opening or rendering malicious documents, user awareness training is critical; employees should be educated to avoid opening attachments from untrusted sources and to disable automatic macro execution where possible. Additionally, deploying application control solutions that restrict the ability of Office applications to access certain system resources can limit the impact even if an exploit succeeds. Network segmentation and intrusion detection systems configured to monitor for anomalous traffic patterns associated with document parsing exploits can also provide an additional layer of defense against remote exploitation attempts. Regular vulnerability assessments focusing on outdated software versions are essential to maintaining a secure posture against such memory corruption vulnerabilities that continue to pose significant risks in enterprise environments relying heavily on Microsoft Office productivity suites.