CVE-2026-123383: Microsoft Office Outlook heap-based buffer overflow

CVE-2026-123383 · Severity: high · CVSS 8.8 · Published 2026-11-10

Microsoft Outlook, an email and calendar application widely used in enterprises, contains a heap-based buffer overflow vulnerability that could allow an attacker to execute malicious code on a user's system. An attacker can exploit this remotely over a network without requiring any special privileges or user interaction, potentially leading to unauthorized access to the victim's email, calendar data, and ability to control the compromised system.

Technologies: Microsoft Office Outlook. Vendors: Microsoft.

Quick answers

Is CVE-2026-123383 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-123383 being exploited in the wild.
How severe is CVE-2026-123383?
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-2026-123383?
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-2026-123383 attacked?
It is attacked over the network, in a web application.
Am I affected by CVE-2026-123383?
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 exists in Microsoft Outlook that can be triggered remotely over the network. The vulnerability allows an attacker to execute arbitrary code with the privileges of the user running Outlook. No user interaction or authentication is required to exploit this condition.

Affected products

  • Microsoft Office Outlook

Timeline

  • 2026-11-10: disclosed

References

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