CVE-2026-54988: Microsoft Excel Information Disclosure Vulnerability

Overview

Severity
Medium (CVSS 6.1)
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H/E:U/RL:O/RC:C
Category
Information Disclosure
Exploit Status
Not Exploited
Exploitation Likelihood
Unlikely
Patch Tuesday
2026-Jul
Released
2026-07-14

Description

Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.

FAQ

Is the Preview Pane an attack vector for this vulnerability? No, the Preview Pane is not an attack vector. According to the CVSS metrics, exploitation results in a small loss of confidentiality (C:L), no integrity impact (I:N), and high availability impact (A:H). What does this mean? This means that an attacker could potentially see a small amount of information they should not have access to, but they cannot change data or system settings. The primary impact is that the affected service could stop working or crash, which may temporarily disrupt normal system operations. What type of information could be disclosed by this vulnerability? An attacker who successfully exploited this vulnerability could potentially read small portions of heap memory. According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do? An attacker must send a user a malicious Office file and convince them to open it.

Affected Products (14)

Microsoft Office

  • Microsoft Office 365 for Mac
  • Office Online Server
  • Microsoft Office 2019 for 32-bit editions
  • Microsoft Office 2019 for 64-bit editions
  • Microsoft 365 Apps for Enterprise for 32-bit Systems
  • Microsoft 365 Apps for Enterprise for 64-bit Systems
  • Microsoft Office LTSC for Mac 2021
  • Microsoft Office LTSC 2021 for 64-bit editions
  • Microsoft Office LTSC 2021 for 32-bit editions
  • Microsoft Office LTSC 2024 for 32-bit editions
  • Microsoft Office LTSC 2024 for 64-bit editions
  • Microsoft Office LTSC for Mac 2024
  • Microsoft Excel 2016 (32-bit edition)
  • Microsoft Excel 2016 (64-bit edition)

Security Updates (4)

Acknowledgments

Haein Lee with KAIST Hacking Lab

Revision History

  • 2026-07-14: Information published.