---
id: CVE-2025-64666
title: >-
  Improper input validation in Microsoft Exchange Server allows an authorized
  attacker to elevate privileges over a network.
summary: >-
  Improper input validation in Microsoft Exchange Server allows an authorized
  attacker to elevate privileges over a network.
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-20
vendor: microsoft
product: exchange_server
affected:
  - exchange_server = 2016
  - exchange_server = 2019
  - exchange_server_subscription_edition < 15.02.2562.035
patched:
  - exchange_server_subscription_edition 15.02.2562.035
published: '2025-12-09'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T21:10:00.183'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-64666'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-64666'
    label: secure@microsoft.com
tags:
  - nvd
epss: 0.0102
epssPercentile: 0.62645
ingestedAt: '2026-10-14T21:57:04.763Z'
---

## Overview

Improper input validation in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.

## Affected

- `exchange_server = 2016`
- `exchange_server = 2019`
- `exchange_server_subscription_edition < 15.02.2562.035`

## Remediation

Upgrade past the affected range:

- `exchange_server_subscription_edition 15.02.2562.035`