---
id: "CVE-2020-0688"
kind: "vulnerability"
aliases: ["CVE-2020-0688"]
title: "Microsoft Exchange Server: Microsoft Exchange Server Validation Key Remote Code Execution Vulnerability"
severity: "critical"
cvss: 9.0
epss: 0.99962
exploited: true
status: "open"
category: "vendor"
products: [{"name": "Microsoft Exchange Server", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exchange-server", "exploited", "on-premises", "ransomware", "vendor", "windows"]
not_affected_if: ["exchange-online", "patched-server"]
published_at: "2020-02-11T22:15:15+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:34+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-0688", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2020-0688", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-0688", "first_seen_at": "2026-10-23T21:57:34+00:00"}]
---

# Microsoft Exchange Server: Microsoft Exchange Server Validation Key Remote Code Execution Vulnerability

Microsoft Exchange Server installs with a static validation key shared across installations, so an attacker who knows the key can forge the ViewState data the server trusts. This lets an authenticated attacker run code 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 ?

## Fix

Apply the Microsoft update for CVE-2020-0688 per vendor instructions (CISA KEV required action); the specific build number is not in the sources.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-0688
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2020-0688
- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2020-0688

## From the sources

A remote code execution vulnerability exists in Microsoft Exchange software when the software fails to properly handle objects in memory, aka 'Microsoft Exchange Memory Corruption Vulnerability'.

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