CVE-2026-80073 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 address that lies outside the boundaries of the intended buffer or array structure. In the context of Outlook, this defect is typically triggered by processing specially crafted input files or network packets designed to exploit parsing logic errors within the application's message handling subsystems. The root cause often stems from insufficient validation of boundary conditions when calculating offsets for reading data structures such as email headers, attachments, or rich text formatting elements. When an attacker crafts a malicious payload that manipulates these offset calculations, they can force Outlook to read memory locations beyond the allocated buffer space. This behavior violates fundamental principles of safe memory management and represents a classic instance of improper input validation leading to information disclosure.
From a technical perspective, out-of-bounds reads are particularly dangerous because they allow an attacker to leak sensitive data from the process's virtual address space without necessarily achieving code execution immediately. The disclosed information may include stack canaries, pointers to other memory regions, or even plaintext contents of previously processed emails and user credentials stored in memory buffers. This capability significantly lowers the barrier for further exploitation stages, as leaked memory addresses can be used to bypass security mitigations such as Address Space Layout Randomization (ASLR). By obtaining these internal references, an attacker gains a deeper understanding of the application's runtime environment, which is crucial for developing reliable exploit chains that lead to remote code execution. The vulnerability affects the confidentiality integrity and availability aspects of information systems by exposing private user data and potentially destabilizing the application through subsequent memory corruption attempts based on leaked pointers.
The operational impact of this vulnerability is severe due to its network-based nature. Since Outlook frequently processes emails received over standard protocols like SMTP, IMAP, or MAPI, an attacker does not need physical access to the target machine nor do they require user interaction beyond opening a malicious message in some configurations. This remote triggerability makes it highly attractive for automated scanning campaigns and targeted phishing attacks where users are tricked into viewing compromised messages. The exposure of internal memory contents can lead to identity theft, corporate espionage, or further compromise of connected network resources if the leaked data includes authentication tokens or session cookies. Organizations relying on Outlook for critical communications face significant risks regarding regulatory compliance and data protection mandates due to this potential leakage of confidential information through a widely deployed client application.
To mitigate these risks, immediate patching is essential as Microsoft releases security updates that address memory management errors in their software products. Administrators should ensure that all instances of Office Outlook are updated with the latest cumulative patches provided by Microsoft Security Response Center. In environments where patching cannot be applied immediately, network-level controls such as deep packet inspection firewalls can help detect and block malformed packets attempting to exploit this specific parsing flaw. Additionally, implementing application whitelisting or restricting macro execution policies can reduce the attack surface associated with Outlook's scripting capabilities which might otherwise facilitate exploitation of memory corruption bugs. Users should also be educated on recognizing suspicious email sources and avoiding interaction with unexpected attachments or rich text content from untrusted senders to minimize exposure to crafted payloads designed to trigger this out-of-bounds read condition.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) category CWE-125, which defines Out-of-Bounds Read as a weakness where software reads data past the end or before the beginning of the intended buffer. It also maps to MITRE ATT&CK techniques related to Initial Access and Credential Access, specifically those involving phishing for information or exploiting vulnerabilities in client applications. Understanding these mappings helps security teams prioritize remediation efforts based on standardized threat intelligence frameworks. The persistence of such flaws highlights the importance of rigorous code review processes focusing on boundary checks and memory safety during software development lifecycles. Continuous monitoring for anomalous network traffic patterns indicative of exploitation attempts remains a vital component of defense-in-depth strategies against this class of vulnerabilities in enterprise environments utilizing Microsoft Office suites.