CVE-2026-88195 in Excel
Summary
by MITRE • 10/14/2026
Buffer over-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 involves a buffer over-read condition within the core processing engine of Microsoft Office Excel, specifically affecting how data structures are accessed during file parsing or rendering operations. A buffer over-read occurs when software reads beyond the allocated boundaries of a memory buffer, typically due to insufficient validation of input length against the size of the destination buffer. In this context, an attacker can craft a malicious document containing specially formatted content that triggers Excel to access memory locations outside the intended scope. This improper boundary check allows the application to retrieve sensitive data stored in adjacent memory regions, which may contain credentials, session tokens, or other confidential information previously loaded into the process space by legitimate applications or system components.
From an operational perspective, this flaw poses a significant risk of unauthorized information disclosure over a network if the vulnerability is exploited through remote vectors such as email attachments or web-hosted documents. An attacker does not need to execute arbitrary code on the target machine but can instead leverage the memory leak to exfiltrate data remotely. The impact extends beyond simple data leakage, as disclosed memory contents can be used for further reconnaissance, privilege escalation, or crafting more sophisticated attacks against other systems within the same network perimeter. This type of vulnerability undermines the confidentiality integrity pillar of information security and can lead to severe compliance violations depending on the nature of the exposed data.
The technical root cause aligns with CWE-126, which classifies buffer over-read vulnerabilities where a program reads past the end of an allocated memory block. In complex applications like Excel, this often stems from legacy code paths or insufficient bounds checking in functions that handle variable-length inputs such as embedded objects, formulas, or binary formats. The lack of rigorous validation allows crafted payloads to manipulate pointer arithmetic, causing the application to interpret unrelated memory segments as valid data structures. This behavior is particularly dangerous because it can occur silently without crashing the application, making detection by standard antivirus signatures difficult and allowing attackers ample time to extract valuable information before any anomaly is noticed.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Organizations should immediately apply vendor-provided security patches that address the specific memory access flaws in Excel versions affected by this vulnerability. Administrators should enforce strict email filtering policies to block suspicious attachments from unknown senders and disable automatic macro execution where possible, as these are common initial attack vectors for delivering malicious documents. Furthermore, implementing application whitelisting can prevent unauthorized executables or scripts associated with exploitation attempts from running on endpoints.
Long-term resilience requires adopting secure coding practices that emphasize input validation and memory safety. Developers should utilize static analysis tools to detect potential buffer over-reads during the software development lifecycle and employ dynamic testing methods such as fuzzing to identify edge cases in file parsing logic. Additionally, enabling Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) can mitigate the impact of exploitation by making it harder for attackers to predict memory layouts or execute injected code, although these controls do not prevent the information disclosure itself. Continuous monitoring of endpoint behavior for unusual network connections originating from office applications can also help in early detection of active exploitation attempts.
This vulnerability is often associated with ATT&CK technique T1005, which covers Data from Local System, specifically under sub-techniques related to file and directory discovery or memory scraping depending on the exact mechanism used by the exploit code. Understanding this mapping helps security teams prioritize response efforts based on known adversary behaviors observed in real-world campaigns targeting productivity software. By treating such vulnerabilities as critical risks requiring immediate patching and enhanced monitoring, organizations can significantly reduce their attack surface against sophisticated threat actors who rely on information gathering phases to advance their intrusion activities.