CVE-2026-54988 in Office
Summary
by MITRE • 07/14/2026
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 07/14/2026
This vulnerability represents a critical out-of-bounds read flaw within Microsoft Office Excel that enables local attackers to extract sensitive information from memory locations outside the intended data boundaries. The technical implementation involves improper input validation and memory access controls within the spreadsheet parsing engine, where Excel fails to properly bounds-check array accesses when processing malformed or specially crafted Excel files. Such flaws typically arise from inadequate defensive programming practices and insufficient boundary checks during data processing operations.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially expose sensitive data including encryption keys, user credentials, application memory contents, or other confidential information stored in adjacent memory regions. Attackers can leverage this weakness by crafting malicious Excel files that trigger the out-of-bounds read condition when opened or processed by vulnerable versions of Excel. The vulnerability aligns with CWE-129, which addresses improper validation of length of input buffers, and more specifically with CWE-787, concerning out-of-bounds write operations that can lead to information disclosure through memory access violations.
From an attack perspective, this vulnerability falls under the ATT&CK technique T1059.005 for command and scripting interpreter, as attackers may use the disclosed information to further compromise systems or escalate privileges. The local nature of the attack means that exploitation typically requires physical access or the ability to execute malicious files within the target environment, though successful exploitation could enable more sophisticated attacks including privilege escalation or lateral movement. Security professionals should note that this vulnerability represents a significant risk in enterprise environments where Excel files are frequently shared and opened by multiple users.
Mitigation strategies must include immediate patching of affected Office versions, implementation of strict file validation policies for Excel documents, and deployment of application whitelisting controls to prevent execution of untrusted spreadsheet files. Organizations should also consider network segmentation and access controls to limit the potential impact of successful exploitation. The vulnerability demonstrates the importance of robust memory safety practices in office productivity applications and highlights the need for continuous security testing of document parsing engines against various input conditions. Regular updates to Microsoft Office products remain essential, as this type of vulnerability often requires vendor-provided patches that address the underlying memory access control mechanisms.