CVE-2026-70328 in Office
Summary
by MITRE • 08/12/2026
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 • 08/12/2026
This vulnerability represents a critical out-of-bounds read flaw within Microsoft Office Excel that enables remote attackers to extract sensitive information from affected systems. The issue manifests when Excel processes specially crafted spreadsheet files, potentially allowing adversaries to access memory locations beyond the intended buffer boundaries. Such vulnerabilities typically arise from insufficient input validation and bounds checking mechanisms within the application's parsing logic for file formats like xls or xlsx. The technical implementation involves the application failing to properly verify array indices or data structure limits during spreadsheet rendering, creating opportunities for information disclosure attacks.
The operational impact of this vulnerability extends beyond simple data exposure, as attackers can potentially gather system memory contents including credentials, encryption keys, or other confidential data. This type of flaw falls under the Common Weakness Enumeration category of CWE-125, which specifically addresses out-of-bounds read conditions that can lead to information disclosure and potential privilege escalation. The vulnerability enables adversaries to perform reconnaissance activities without direct system access, making it particularly dangerous for enterprise environments where Excel documents are frequently shared across networks. Attackers typically exploit this weakness by crafting malicious spreadsheet files that trigger the vulnerable code path when opened by an unsuspecting user.
Security professionals should implement immediate mitigations including keeping Microsoft Office updated with the latest security patches, implementing network segmentation to limit exposure, and deploying email filtering solutions to block suspicious spreadsheet attachments. The vulnerability aligns with ATT&CK technique T1566 which covers spearphishing attacks through malicious documents, making it a prime target for targeted campaigns. Organizations should also consider disabling automatic execution of macros in Excel environments, as this can prevent exploitation of related attack vectors. Additionally, network monitoring solutions should be configured to detect unusual data access patterns that might indicate information disclosure attempts. The risk assessment for this vulnerability should include consideration of the attack surface within corporate networks where Excel documents are commonly shared via email or file transfer protocols, particularly in environments with insufficient security controls.
This type of information disclosure vulnerability demonstrates the ongoing challenges in securing complex office productivity applications where extensive parsing logic creates numerous potential attack surfaces. The remediation approach requires not only patch management but also comprehensive security awareness training for end users to recognize suspicious document attachments. Organizations implementing zero-trust security models should particularly focus on validating all spreadsheet content before processing, as this vulnerability can be exploited through automated means when documents are opened in automated environments. The threat landscape continues to evolve with adversaries increasingly targeting office productivity applications due to their widespread use and the sophisticated nature of modern exploitation techniques.