---
id: "CVE-2025-64394"
kind: "vulnerability"
aliases: ["CVE-2025-64394"]
title: "Veeam Backup for Microsoft 365: local users can write files as SYSTEM"
severity: "medium"
cvss: 4.3
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["backup", "infrastructure", "veeam", "windows"]
not_affected_if: ["no-local-untrusted-users"]
published_at: "2026-10-27T17:16:53+00:00"
first_seen_at: "2026-10-27T17:32:44+00:00"
updated_at: "2026-10-27T17:34:59+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-64394", "first_seen_at": "2026-10-27T17:32:44+00:00"}]
---

# Veeam Backup for Microsoft 365: local users can write files as SYSTEM

During installation of Veeam Backup for Microsoft 365, a low-privileged local user can write arbitrary files with SYSTEM privileges. An attacker can use this to escalate privileges to SYSTEM or crash the service.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Veeam Backup for Microsoft 365 version in Programs and Features or the product's About page
- unknown

## Fix

- Update Veeam Backup for Microsoft 365 to a fixed build from Veeam's advisory
- unknown

## Timeline

- 2026-10-27T17:32:44+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2025-64394

## From the sources

A vulnerability allowing a low-privileged local user to write arbitrary files with SYSTEM privileges during the installation of Veeam Backup for Microsoft 365, which can lead to privilege escalation or denial of service.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_