CVE-2026-80091 in Office
Summary
by MITRE • 09/09/2026
Use of uninitialized resource in Microsoft Office 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 the improper initialization of resources within Microsoft Office applications, which can lead to the disclosure of sensitive information to unauthorized parties who have access to the local system or potentially over a network depending on specific exploitation vectors. This class of flaw is fundamentally rooted in how memory management and object lifecycle handling are executed during the processing of complex document structures or embedded objects. When an application fails to properly initialize variables, pointers, or data structures before they are read or utilized, it may expose residual data from previous operations that was not cleared from memory. In the context of Microsoft Office, this often manifests when parsing specially crafted files such as Word documents, Excel spreadsheets, or PowerPoint presentations containing malformed metadata, embedded OLE objects, or specific formatting codes that trigger unexpected code paths where these uninitialized resources are accessed rather than initialized with safe default values.
From a technical perspective, this flaw aligns closely with CWE-457, which defines the use of an uninitialized variable as a software weakness. The operational mechanism typically involves the application allocating memory for a data structure but failing to zero out or assign initial values before proceeding with logic that reads from those locations. If the allocated memory previously held sensitive information such as credentials, session tokens, internal file paths, or other user-specific data, and this content is not overwritten by subsequent operations, it may be inadvertently included in error messages, log files, network packets generated during auto-save features, or even displayed directly to a local attacker who can trigger the specific parsing routine. While the prompt mentions disclosure over a network, such vulnerabilities are most commonly exploited locally through crafted documents that cause the application to leak memory contents via crash dumps, clipboard operations, or inter-process communication channels rather than direct remote code execution or network exfiltration without additional helper components.
The impact of this vulnerability is primarily categorized under information disclosure, which compromises the confidentiality aspect of the CIA triad. An attacker who can trick a user into opening a malicious document could potentially extract sensitive data stored in memory by Microsoft Office processes. This might include previously opened documents' content, cached authentication tokens for cloud services like OneDrive or SharePoint, or internal system configuration details that aid in further reconnaissance. Although direct remote exploitation over the network is less common without additional vectors such as server-side processing of uploaded files, the risk remains significant because it allows an attacker to gain insights into the victim's environment and potentially escalate privileges if combined with other vulnerabilities like buffer overflows or type confusion issues within the same component.
In terms of threat modeling, this vulnerability can be mapped to MITRE ATT&CK techniques related to Collection and Exfiltration, specifically those involving local data staging or memory scraping. Attackers might leverage tools that monitor process memory for specific patterns indicative of successful exploitation, such as strings resembling API keys or personal identifiable information appearing in unexpected locations within the Office application's address space. The lack of proper initialization represents a failure in secure coding practices where defensive programming principles were not applied to ensure data integrity and confidentiality during runtime operations.
Mitigation strategies focus on both immediate remediation and long-term architectural improvements. Microsoft typically addresses such issues through security updates that patch the specific parsing routines responsible for handling uninitialized resources, ensuring that all memory allocations are properly zeroed or initialized before use. Users should apply these patches promptly to close the window of opportunity for exploitation. Additionally, organizations can implement application control policies using tools like AppLocker or Windows Defender Application Control to restrict the execution of untrusted scripts and macros within Office applications, thereby reducing the attack surface available to an adversary attempting to trigger the vulnerability. Enabling Protected View by default ensures that documents downloaded from the internet are opened in a sandboxed environment with limited permissions, which can prevent certain types of memory corruption or information leakage exploits from affecting the host system's sensitive data stores.