CVE-2026-80084 in Office
Summary
by MITRE • 09/09/2026
Out-of-bounds read in Microsoft Office Outlook 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 constitutes a critical security flaw within the Microsoft Office Outlook application, specifically manifesting as an out-of-bounds read condition. This type of memory corruption error occurs when software attempts to access data at a memory location that lies outside the boundaries of the intended buffer or array structure. In the context of network-facing applications like Outlook, this defect is particularly dangerous because it can be triggered by processing maliciously crafted content received over a network connection. The root cause typically involves insufficient validation of input parameters or length checks before accessing memory regions, allowing an attacker to control the offset used for reading data from system memory.
From a technical perspective, out-of-bounds read vulnerabilities are classified under CWE-125 in the Common Weakness Enumeration standard. This category encompasses situations where software reads past the end of a buffer, potentially exposing sensitive information stored adjacent to the intended target area. When Outlook processes specially constructed email messages or calendar items containing malformed data structures, it may calculate an incorrect memory address and retrieve contents from that location. Unlike out-of-bounds writes which can lead to code execution, out-of-bounds reads primarily facilitate information disclosure. The attacker does not gain direct control over the processor instruction pointer but instead extracts arbitrary bytes of memory content back into their controlled environment through the application's response mechanisms or error handling routines.
The operational impact of this vulnerability centers on unauthorized data exfiltration and potential reconnaissance activities against the target organization. An authorized user who receives a maliciously crafted message could inadvertently trigger the flaw, leading to the leakage of sensitive information from the local machine's memory. This disclosed data might include partial contents of other open documents, cached credentials, encryption keys, or internal network configuration details that were previously loaded into RAM but not intended for exposure. While the immediate risk is often limited to confidentiality rather than integrity or availability, such leaks can serve as a precursor to more severe attacks by providing attackers with valuable context about the victim's environment and security posture.
In terms of threat modeling and adversary behavior, this vulnerability aligns with techniques found in the MITRE ATT&CK framework related to Collection via Peripheral Device Removal or potentially Data from Local System if interpreted broadly under information gathering tactics. Specifically, it relates to methods where attackers exploit software flaws to extract data without direct file system access. The attack vector is classified as remote over a network, meaning no physical proximity or local account privileges are required for initial exploitation. However, successful exploitation generally requires social engineering elements such as convincing the user to open a specific email attachment or view a malicious message, placing it in the Execution phase of the kill chain under User Interaction requirements.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary defense is applying the latest security patches released by Microsoft for all affected versions of Outlook and Office suites. These updates typically include bounds checking logic that validates array indices or buffer lengths before memory access operations occur. Organizations should also enforce strict email filtering policies to block suspicious attachments and disable unnecessary features like automatic preview pane rendering if feasible, thereby reducing the attack surface. Additionally, implementing application whitelisting and restricting macro execution can limit the ability of malicious payloads to fully exploit such vulnerabilities even after initial trigger events. Regular vulnerability scanning and penetration testing focused on client-side applications are essential for identifying similar weaknesses before they can be weaponized by threat actors targeting enterprise environments.