# CVE-2026-78515: Microsoft Excel out-of-bounds read information disclosure

Source: https://junglewise.ai/threats/cve-2026-78515-microsoft-excel-out-of-bounds-read-information-disclosure  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-08. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-78515 · Severity: medium · CVSS 6.5 · Published 2026-09-08

Microsoft Excel contains an out-of-bounds read vulnerability that allows an attacker to disclose sensitive information from affected systems over the network. An attacker can exploit this flaw to extract data from Excel spreadsheets or memory without requiring special credentials or user interaction. This could lead to exposure of confidential business data, customer information, or other sensitive content stored in or processed by Excel.

Technologies: [Microsoft Excel](https://junglewise.ai/threats/technologies/excel). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-78515 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78515 being exploited in the wild.

**How severe is CVE-2026-78515?** Medium severity, with a CVSS score of 6.5, published 8 September 2026.

**Which products and versions are affected?** Microsoft Excel.

**Is there a fix for CVE-2026-78515?** 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-2026-78515 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-78515?** Check whether you run Microsoft Excel. 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 out-of-bounds read vulnerability exists in Microsoft Excel's data parsing or processing logic. The vulnerability allows an attacker to read memory beyond intended boundaries, potentially exposing sensitive information such as private keys, credentials, or file contents. The flaw is triggered when processing a specially crafted Excel file sent over the network, with no authentication or user interaction beyond opening the malicious document. An attacker can leverage this to extract confidential data from the affected system. Microsoft has released a security update to address this vulnerability.

## Affected products

- Microsoft Excel

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78515](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78515)

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