CVE-2026-55138: Microsoft Excel Information Disclosure Vulnerability

Overview

Severity
Medium (CVSS 5.5)
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C
Category
Information Disclosure
Exploit Status
Not Exploited
Exploitation Likelihood
Less Likely
Patch Tuesday
2026-Jul
Released
2026-07-14

Description

Untrusted pointer dereference in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.

FAQ

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. Is the Preview Pane an attack vector for this vulnerability? No, the Preview Pane is not an attack vector. 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

  • 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)
  • Microsoft Office 365 for Mac

Security Updates (4)

Acknowledgments

<a href="https://x.com/dnpushme">f4 &amp; Zhiniang Peng with HUST</a>

Revision History

  • 2026-07-14: Information published.