CVE-2026-123384: Microsoft Outlook heap-based buffer overflow

CVE-2026-123384 · Severity: high · CVSS 8.8 · Published 2026-11-10

Microsoft Outlook, an email and calendar application used across organizations, contains a heap-based buffer overflow vulnerability that allows an attacker to execute arbitrary code remotely over a network. An attacker can exploit this without authentication to gain code execution on a victim's system, potentially leading to data theft, malware installation, or system compromise.

Technologies: Microsoft Outlook. Vendors: Microsoft.

Quick answers

Is CVE-2026-123384 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-123384 being exploited in the wild.
How severe is CVE-2026-123384?
High severity, with a CVSS score of 8.8, published 10 November 2026.
Which products and versions are affected?
Microsoft Outlook.
Is there a fix for CVE-2026-123384?
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-2026-123384 attacked?
It is attacked over the network, in a web application.
Am I affected by CVE-2026-123384?
Check whether you run Microsoft 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 can be triggered over the network by an unauthenticated attacker, resulting in arbitrary code execution. The vulnerability lies in memory handling within the application and does not require user interaction. Successful exploitation grants the attacker code execution in the context of the Outlook process.

Affected products

  • Microsoft Outlook

Timeline

  • 2026-11-10: disclosed

References

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