---
id: "CVE-2021-31196"
kind: "vulnerability"
aliases: ["CVE-2021-31196"]
title: "Microsoft Exchange Server Remote Code Execution Vulnerability"
severity: "high"
cvss: 7.2
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", "microsoft", "self-hosted", "vendor"]
not_affected_if: ["exchange-online", "unknown"]
published_at: "2021-07-14T18:15:09+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T22:29:05+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-31196", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-31196", "first_seen_at": "2026-10-23T22:29:05+00:00"}]
---

# Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange Server has an information disclosure flaw that CISA lists as known exploited. The description also says it allows remote code execution, so the sources conflict on impact.

_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 Microsoft mitigations per vendor instructions, or stop using the product if mitigations are unavailable (per CISA required action).

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-31196
- 2026-10-23T22:29:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-31196

## From the sources

Microsoft Exchange Server contains an information disclosure vulnerability that allows for remote code execution.

CISA required action: Apply mitigations per vendor instructions 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_