# CVE-2025-64394: Veeam Backup for Microsoft 365 privilege escalation during installation

Source: https://junglewise.ai/threats/cve-2025-64394-a-vulnerability-allowing-a-low-privileged-local-user-to-write  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2025-64394 · Severity: info · Published 2026-10-27

Veeam Backup for Microsoft 365 is software that protects Office 365 data by creating backups. A vulnerability in the installation process allows a low-privileged local user to write files with SYSTEM-level permissions, enabling privilege escalation or causing the application to fail. An attacker must already have local access and user interaction during setup is required to exploit this flaw.

Technologies: [Veeam Backup for Microsoft 365](https://junglewise.ai/threats/technologies/backup-for-microsoft-365). Vendors: [Veeam](https://junglewise.ai/threats/vendors/veeam).

## Quick answers

**Is CVE-2025-64394 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-64394 being exploited in the wild.

**How severe is CVE-2025-64394?** Informational severity, published 27 October 2026.

**Which products and versions are affected?** Veeam Backup for Microsoft 365 8.6.0.1102 and all earlier version 8 builds.

**Is there a fix for CVE-2025-64394?** Yes: fixed in Veeam Backup for Microsoft 365 8.6.0.1102. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2025-64394 attacked?** It is attacked with local access, in a hosted service.

**Am I affected by CVE-2025-64394?** Check whether you run Veeam Backup for Microsoft 365 at an affected version. 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.

## How to fix

- Fixed in Veeam Backup for Microsoft 365 8.6.0.1102

## Technical details

This vulnerability exists during Veeam Backup for Microsoft 365 installation and allows a low-privileged local user to write arbitrary files with SYSTEM privileges through an insecure file write operation during the installation process. The attack requires local access, low privileges, and user interaction, but results in privilege escalation or denial of service. A fix is available in version 8.6.0.1102 and later.

## Affected products

- Veeam Backup for Microsoft 365 8.6.0.1102 and all earlier version 8 builds

## Timeline

- 2026-10-27: disclosed

## References

- [https://www.veeam.com/kb4957](https://www.veeam.com/kb4957)

## Related threats

- [Veeam Backup for Microsoft 365 REST API authentication bypass](https://junglewise.ai/threats/cve-2026-106078-a-vulnerability-allowing-an-unauthenticated-attacker-to-bypass)
- [Veeam Backup for Microsoft 365 arbitrary file read in Admin role](https://junglewise.ai/threats/cve-2026-106077-a-vulnerability-allowing-a-user-with-the-veeam-backup-for)
- [Veeam Backup for Microsoft 365 SQL injection in configuration database](https://junglewise.ai/threats/cve-2026-106076-a-vulnerability-allowing-an-authenticated-organization-transfer)