CVE-2026-88184 in Excel
Summary
by MITRE • 10/14/2026
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Excel application, specifically categorized as an out-of-bounds read error. This type of memory corruption issue arises when software attempts to access data at a memory location that is outside the boundaries of the intended buffer or array structure. In the context of Excel, this typically occurs during the parsing and rendering of complex spreadsheet files containing specially crafted formulas, embedded objects, or malformed binary structures. When an attacker crafts a malicious document designed to exploit this specific condition, they can trigger the application to read memory contents that were not allocated for its use. This deviation from standard memory access protocols allows the execution environment to expose internal data states that are otherwise protected by operating system security boundaries and sandboxing mechanisms inherent in modern office suites.
From an operational perspective, the primary impact of this vulnerability is information disclosure rather than immediate code execution or remote control. By leveraging the out-of-bounds read condition, an unauthorized attacker can potentially extract sensitive data residing in adjacent memory regions. This may include cryptographic keys, session tokens, passwords, or other confidential user information stored temporarily by Excel during document processing. The ability to disclose this information over a network significantly elevates the severity of the threat, as it enables remote exploitation without requiring physical access to the target machine. An attacker could distribute such malicious files via phishing campaigns, compromised websites, or shared drives, relying on social engineering to trick users into opening them. Once opened, the exploit triggers silently in the background, allowing data exfiltration before any obvious signs of compromise are detected by end-users or standard security monitoring tools.
This vulnerability aligns with Common Weakness Enumeration (CWE) identifier CWE-125, which defines out-of-bounds read as a flaw where software reads past the end of an allocated buffer. The exploitation technique is consistent with ATT&CK tactic T1005, specifically sub-technique T1005.001 for Data from Local System, and potentially T1048 if network-based exfiltration methods are employed to transmit the stolen data externally. Understanding these mappings helps security teams prioritize remediation efforts based on established industry frameworks that categorize risks by their potential impact on confidentiality, integrity, and availability. The presence of such a flaw indicates gaps in input validation routines within Excel's file parsing engine, highlighting the need for rigorous boundary checks when handling untrusted external data sources.
To mitigate this risk, organizations must ensure that all Microsoft Office components are updated to the latest versions containing the provided security patches. These updates typically include enhanced memory safety features and stricter validation logic designed to detect and abort operations involving invalid memory accesses before they can result in information leakage. Additionally, implementing application control policies such as AppLocker or Windows Defender Application Control can restrict Excel from executing scripts or loading add-ins that might facilitate exploitation vectors. Users should be trained to recognize suspicious file attachments and avoid opening documents from untrusted sources. Network segmentation and data loss prevention solutions can also help detect anomalous outbound traffic patterns associated with information exfiltration attempts, providing an additional layer of defense against the successful deployment of this exploit in enterprise environments.