---
id: "CVE-2023-21529"
kind: "vulnerability"
aliases: ["CVE-2023-21529"]
title: "Microsoft Exchange Server Remote Code Execution Vulnerability"
severity: "high"
cvss: 8.8
epss: null
exploited: true
status: "open"
category: "vendor"
products: [{"name": "Microsoft Exchange Server", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "microsoft exchange server", "fixed": [], "affected": "= 2013", "ecosystem": "vendor"}, {"name": "microsoft exchange server", "fixed": [], "affected": "= 2016", "ecosystem": "vendor"}, {"name": "microsoft exchange server", "fixed": [], "affected": "= 2019", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exchange-server", "exploited", "on-prem-exchange", "ransomware", "vendor", "windows"]
not_affected_if: ["auth-required", "exchange-online"]
published_at: "2023-02-14T20:15:11+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T23:44:51+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2023-21529", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-21529", "first_seen_at": "2026-10-23T23:44:51+00:00"}]
---

# Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange Server has a deserialization flaw in which untrusted data is processed unsafely. An authenticated attacker can achieve remote code execution on the Exchange server.

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

## Affected

- vendor:Microsoft Exchange Server affected ? fixed ?
- vendor:microsoft exchange server affected = 2013 fixed ?
- vendor:microsoft exchange server affected = 2016 fixed ?
- vendor:microsoft exchange server affected = 2019 fixed ?

## Fix

Apply the mitigations and patches per Microsoft's vendor instructions; the sources do not name specific versions or settings. If mitigations are unavailable, CISA says to discontinue use of the product.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2023-21529
- 2026-10-23T23:44:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2023-21529

## From the sources

Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.

CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

---

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