---
title: "CVE-2021-42321: Microsoft Exchange Server Remote Code… | CubePath"
description: "Microsoft Exchange Server Remote Code Execution Vulnerability"
language: en
source: https://cubepath.com/security/cve/CVE-2021-42321
---

# CVE-2021-42321: Microsoft Exchange Server Remote Code… | CubePath

## Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Official description from the CVE record, published by microsoft. Copyright © 1999-2026 The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-42321)

## Key data

### CVSS 3.1 High 8.8

Score published by microsoft in the CVE record.

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

| Metric                 | Value     | What it means                                                                       |
| ---------------------- | --------- | ----------------------------------------------------------------------------------- |
| Attack vector          | Network   | The vulnerable component can be reached over a network, possibly from the Internet. |
| Attack complexity      | Low       | No special conditions are needed. The attack can be repeated at will.               |
| Privileges required    | Low       | A basic user account is needed.                                                     |
| User interaction       | None      | No action from any user is needed.                                                  |
| Scope                  | Unchanged | The impact stays within the vulnerable component.                                   |
| Confidentiality impact | High      | Serious or total effect on the secrecy of data.                                     |
| Integrity impact       | High      | Serious or total effect on the trustworthiness of data.                             |
| Availability impact    | High      | Serious or total effect on availability.                                            |

CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at [first.org/cvss](https://www.first.org/cvss/) .

### EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.

Score

0.91737 (91.7% probability)

Percentile

99.8%

Scores of

Nov 10, 2026

Model

v2026.06.15

### CISA Known Exploited Vulnerabilities

This CVE is listed in the CISA KEV catalog.

Name in the catalog

Microsoft Exchange Server Remote Code Execution Vulnerability

Added to the catalog

Nov 17, 2021

Federal due date

Dec 1, 2021

Ransomware campaigns

Known use

### CISA assessment as of Jan 3, 2024

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.

Exploitation

Recorded by CISA as active

Automatable

no

Technical impact

total

## Affected products

Products listed in the CVE record, as the CNA published them.

- Microsoft Exchange Server 2016 Cumulative Update 21

  - affected: 15.01.0 up to before 15.01.2308.020
- Microsoft Exchange Server 2016 Cumulative Update 22

  - affected: 15.0.0 up to before 15.01.2375.017
- Microsoft Exchange Server 2019 Cumulative Update 10

  - affected: 15.02.0 up to before 15.02.0792.019
- Microsoft Exchange Server 2019 Cumulative Update 11

  - affected: 15.02.0 up to before 15.02.0986.014

## References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

- [Microsoft Exchange Server Remote Code Execution Vulnerability](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42321)  (msrc.microsoft.com) vendor-advisory patch
- [portal.msrc.microsoft.com/en-US/security-guidance/advisory/…](https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42321)
- [packetstormsecurity.com/files/166153/Microsoft-Exchange-Ser…](http://packetstormsecurity.com/files/166153/Microsoft-Exchange-Server-Remote-Code-Execution.html)
- [packetstormsecurity.com/files/168131/Microsoft-Exchange-Ser…](http://packetstormsecurity.com/files/168131/Microsoft-Exchange-Server-ChainedSerializationBinder-Remote-Code-Execution.html)

## Timeline

1. ID reserved Oct 12, 2021
2. Record published Nov 10, 2021
3. Added to CISA KEV Nov 17, 2021
4. Record last updated Aug 19, 2026

## Look up another CVE

## About CubePath

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:34 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)