# CVE-2026-78525: Microsoft Office Outlook use-after-free remote code execution

Source: https://junglewise.ai/threats/cve-2026-78525-microsoft-office-outlook-use-after-free-remote-code-execution  
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-2026-78525 · Severity: high · CVSS 8.8 · Published 2026-09-08

Microsoft Outlook is an email and calendar client used across enterprise and consumer environments. A use-after-free memory vulnerability in Outlook allows an attacker to execute arbitrary code on a user's machine remotely, potentially compromising sensitive email data, calendar information, and gaining a foothold into the network.

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

## Quick answers

**Is CVE-2026-78525 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78525 being exploited in the wild.

**How severe is CVE-2026-78525?** High severity, with a CVSS score of 8.8, published 8 September 2026.

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

**Is there a fix for CVE-2026-78525?** 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-2026-78525 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-78525?** 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 use-after-free vulnerability exists in Microsoft Office Outlook where freed memory is accessed or reused improperly, leading to memory corruption and arbitrary code execution. The vulnerability can be triggered over a network without requiring authentication or special privileges. An attacker can craft a malicious email or calendar item that exploits this flaw when processed by Outlook. Successful exploitation results in remote code execution in the context of the user running Outlook. Microsoft has released patches to address this vulnerability.

## Affected products

- Microsoft Office Outlook

## Timeline

- 2026-09-08: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78525](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78525)

## Related threats

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- [Microsoft Office Outlook untrusted pointer dereference](https://junglewise.ai/threats/cve-2026-123382-untrusted-pointer-dereference-in-microsoft-office-outlook-allows)