# CVE-2026-55138: Microsoft Excel untrusted pointer dereference information disclosure Source: https://junglewise.ai/threats/cve-2026-55138-microsoft-excel-untrusted-pointer-dereference-information Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats Published: 2026-07-14. Updated: 2026-07-14 License: CC BY 4.0 with a link back CVE-2026-55138 · Severity: medium · CVSS 5.5 · Published 2026-07-14 A security vulnerability exists in Microsoft Excel, the widely used spreadsheet application. An attacker could exploit this flaw to gain unauthorized access to sensitive information on a user's computer. To be successful, an attacker would typically need to trick a user into opening a specially crafted Excel file. Technologies: [Microsoft 365 Apps for Enterprise](https://junglewise.ai/threats/technologies/365-apps-for-enterprise), [Microsoft Excel 2016](https://junglewise.ai/threats/technologies/excel-2016), [Microsoft Office 2019](https://junglewise.ai/threats/technologies/office-2019), [Microsoft Office 365 for Mac](https://junglewise.ai/threats/technologies/office-365-for-mac), [Microsoft Office LTSC 2021](https://junglewise.ai/threats/technologies/office-ltsc-2021), [Microsoft Office LTSC 2024](https://junglewise.ai/threats/technologies/office-ltsc-2024), [Microsoft Office LTSC for Mac 2021](https://junglewise.ai/threats/technologies/office-ltsc-for-mac-2021), [Microsoft Office LTSC for Mac 2024](https://junglewise.ai/threats/technologies/office-ltsc-for-mac-2024), [Microsoft Office Online Server](https://junglewise.ai/threats/technologies/office-online-server). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft). ## Quick answers **Is CVE-2026-55138 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55138 being exploited in the wild. **How severe is CVE-2026-55138?** Medium severity, with a CVSS score of 5.5, published 14 July 2026. **Which products and versions are affected?** Microsoft 365 Apps for Enterprise versions prior to July 2026 updates; Microsoft Excel 2016 versions prior to 16.0.5561.1001; Microsoft Office 2019 versions prior to July 2026 updates; Microsoft Office 365 for Mac versions prior to 16.111.26071215; and 5 more. **Is there a fix for CVE-2026-55138?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it. **How is CVE-2026-55138 attacked?** It is attacked with local access, in a network appliance. **Am I affected by CVE-2026-55138?** Check whether you run Microsoft 365 Apps for Enterprise, Microsoft Excel 2016, Microsoft Office 2019 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you. ## Technical details An untrusted pointer dereference vulnerability (CWE-822) exists in multiple versions of Microsoft Excel and Office products. The flaw is triggered when the application processes a malformed file, leading to an out-of-bounds memory access. An attacker can exploit this by convincing a user to open a malicious document, which could result in the disclosure of sensitive memory contents. This is a local attack requiring user interaction, and while it does not allow for direct code execution, it can be used to bypass security mitigations like ASLR. Microsoft has released security updates to address this issue across affected platforms including Windows and macOS. ## Affected products - Microsoft Microsoft 365 Apps for Enterprise versions prior to July 2026 updates - Microsoft Microsoft Excel 2016 versions prior to 16.0.5561.1001 - Microsoft Microsoft Office 2019 versions prior to July 2026 updates - Microsoft Microsoft Office 365 for Mac versions prior to 16.111.26071215 - Microsoft Microsoft Office LTSC 2021 versions prior to July 2026 updates - Microsoft Microsoft Office LTSC 2024 versions prior to July 2026 updates - Microsoft Microsoft Office LTSC for Mac 2021 versions prior to 16.111.26071215 - Microsoft Microsoft Office LTSC for Mac 2024 versions prior to 16.111.26071215 - Microsoft Office Online Server versions prior to 16.0.10417.20175 ## Timeline - 2026-07-14: disclosed - 2026-07-14: advisory ## References - [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55138](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55138) ## Related threats - [Microsoft Office Excel out-of-bounds read in parsing](https://junglewise.ai/threats/cve-2026-105718-out-of-bounds-read-in-microsoft-office-excel-allows-an) - [Microsoft Office Excel use-after-free remote code execution](https://junglewise.ai/threats/cve-2026-100212-use-after-free-in-microsoft-office-excel-allows-an-unauthorized) - [Microsoft Office Excel heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-100210-heap-based-buffer-overflow-in-microsoft-office-excel-allows-an) - [Out-of-bounds read in Microsoft Office Word allows an unauthorized attacker to disclose information locally.](https://junglewise.ai/threats/cve-2026-70310-out-of-bounds-read-in-microsoft-office-word-allows-an) - [Microsoft Office out-of-bounds read information disclosure](https://junglewise.ai/threats/cve-2026-56195-microsoft-office-out-of-bounds-read-information-disclosure)