# CVE-2026-123376: Microsoft Office Outlook heap-based buffer overflow

Source: https://junglewise.ai/threats/cve-2026-123376-heap-based-buffer-overflow-in-microsoft-office-outlook-allows-an  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-10. Updated: 2026-11-10  
License: CC BY 4.0 with a link back

CVE-2026-123376 · Severity: high · CVSS 8.8 · Published 2026-11-10

Microsoft Outlook is an email and calendar management application used by millions of businesses and individuals. A heap-based buffer overflow vulnerability allows an attacker to execute arbitrary code remotely without requiring user credentials, potentially leading to unauthorized access, data theft, or malware installation.

Technologies: [Microsoft Office Outlook](https://junglewise.ai/threats/technologies/office-outlook). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-123376 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-123376 being exploited in the wild.

**How severe is CVE-2026-123376?** High severity, with a CVSS score of 8.8, published 10 November 2026.

**Which products and versions are affected?** Microsoft Office Outlook.

**Is there a fix for CVE-2026-123376?** 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-2026-123376 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-123376?** Check whether you run Microsoft Office Outlook. 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

A heap-based buffer overflow in Microsoft Outlook permits remote code execution via network-based attack vectors. The vulnerability does not require authentication and allows an attacker to achieve arbitrary code execution in the context of the Outlook process.

## Affected products

- Microsoft Office Outlook

## Timeline

- 2026-11-10: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-123376](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-123376)

## Related threats

- [Microsoft Office Outlook path traversal in pathname handling](https://junglewise.ai/threats/cve-2026-124228-improper-limitation-of-a-pathname-to-a-restricted-directory-path)
- [Microsoft Office Outlook use of uninitialized resource code execution](https://junglewise.ai/threats/cve-2026-124227-use-of-uninitialized-resource-in-microsoft-office-outlook-allows)
- [Microsoft Office Outlook user warning spoofing vulnerability](https://junglewise.ai/threats/cve-2026-124194-microsoft-office-outlook-missing-user-interaction-for)
- [Microsoft Office Outlook heap-based buffer overflow](https://junglewise.ai/threats/cve-2026-123383-heap-based-buffer-overflow-in-microsoft-office-outlook-allows-an)
- [Microsoft Office Outlook untrusted pointer dereference](https://junglewise.ai/threats/cve-2026-123382-untrusted-pointer-dereference-in-microsoft-office-outlook-allows)