---
title: "CVE-2021-31196: Microsoft Exchange Server Information Disclosure Vulnerability"
url: https://erroneo.us/security/cve/CVE-2021-31196/
description: "CVE-2021-31196 (Microsoft Exchange Server): Exploited in the wild (CISA KEV). Microsoft Exchange Server Remote Code Execution Vulnerability"
type: vulnerability-record
section: "Security Digest"
date_published: 2021-07-14
date_modified: 2026-08-10
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2021-31196"
kev: true
cvss: 7.2
epss: 0.54056
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2021-31196: Microsoft Exchange Server Information Disclosure Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Microsoft Exchange Server. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2024-08-21, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2024-09-11 ; treat that as the outer limit, not the target.
- EPSS 54.1% , percentile 99: FIRST’s model estimates a 54.1% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Needs an account (high (admin)). Exposure depends on who can log in.

## What it is

Microsoft Exchange Server Remote Code Execution Vulnerability

## Affected products (CVE record)

- Microsoft Microsoft Exchange Server 2013 Cumulative Update 23: 15.00.0 < 15.00.1497.023
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 20: 15.01.0 < 15.01.2242.012
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 21: 15.01.0 < 15.01.2308.014
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 10: 15.02.0 < 15.02.0922.013
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 9: 15.02.0 < 15.02.0858.015

## Severity

- microsoft CVSS 3.1: 7.2 `CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`

## Exploitation

- CISA KEV: added 2024-08-21; federal due date 2024-09-11. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 54.06% probability of exploitation activity in the next 30 days; percentile 99.

## Sources

- [Microsoft Exchange Server Remote Code Execution Vulnerability](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-31196)
- [Listed in CISA KEV notes (msrc.microsoft.com)](https://msrc.microsoft.com/update-guide/en-US/advisory/CVE-2021-31196)
- [CVE.org record CVE-2021-31196](https://www.cve.org/CVERecord?id=CVE-2021-31196)
- [NVD entry CVE-2021-31196](https://nvd.nist.gov/vuln/detail/CVE-2021-31196)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31196)
- [portal.msrc.microsoft.com](https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31196)

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Source page: https://erroneo.us/security/cve/CVE-2021-31196/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt