# Exchange Server vulnerabilities

> Exchange Server is made by Microsoft. We track 232 published vulnerabilities in it, across 10 versions. 19 of them are on the list of flaws known to be exploited, the newest added on 13 April 2026. If you run Exchange Server, check your version against the exploited flaws below and patch those first.

Canonical page: https://www.edgeprotect.io/product/microsoft/exchange_server

## At a glance

- **Made by:** [Microsoft](https://www.edgeprotect.io/vendors/microsoft)
- **Published vulnerabilities:** 232
- **Known to be exploited:** 19
- **Versions tracked:** 10
- **Most recently added to the known-exploited list:** [CVE-2023-21529](https://www.edgeprotect.io/what-is/cve-2023-21529), 13 April 2026. We keep watching the list.

## Which versions of Exchange Server do the exploited flaws hit?

Each exploited flaw lists the versions it affects, as published.

- [CVE-2023-21529](https://www.edgeprotect.io/what-is/cve-2023-21529) (Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability): 2013-cumulative_update_23, 2016-cumulative_update_23, 2019-cumulative_update_11, 2019-cumulative_update_12
- [CVE-2021-31196](https://www.edgeprotect.io/what-is/cve-2021-31196) (Microsoft Exchange Server Information Disclosure Vulnerability): 2013-cumulative_update_23, 2016-cumulative_update_20, 2016-cumulative_update_21, 2019-cumulative_update_9, 2019-cumulative_update_10
- [CVE-2024-21410](https://www.edgeprotect.io/what-is/cve-2024-21410) (Microsoft Exchange Server Privilege Escalation Vulnerability): 2016-cumulative_update_23, 2019-cumulative_update_13, 2019-cumulative_update_14
- [CVE-2022-41080](https://www.edgeprotect.io/what-is/cve-2022-41080) (Microsoft Exchange Server Privilege Escalation Vulnerability): 2013-cumulative_update_23, 2016-cumulative_update_22, 2016-cumulative_update_23, 2019-cumulative_update_11, 2019-cumulative_update_12
- [CVE-2022-41040](https://www.edgeprotect.io/what-is/cve-2022-41040) (Microsoft Exchange Server Server-Side Request Forgery Vulnerability): 2013-cumulative_update_23, 2016-cumulative_update_22, 2016-cumulative_update_23, 2019-cumulative_update_11, 2019-cumulative_update_12
- [CVE-2022-41082](https://www.edgeprotect.io/what-is/cve-2022-41082) (Microsoft Exchange Server Remote Code Execution Vulnerability): 2013-cumulative_update_23, 2016-cumulative_update_22, 2016-cumulative_update_23, 2019-cumulative_update_11, 2019-cumulative_update_12
- [CVE-2017-8540](https://www.edgeprotect.io/what-is/cve-2017-8540) (Microsoft Malware Protection Engine Improper Restriction of Operations Vulnerability): 2013, 2016
- [CVE-2018-8581](https://www.edgeprotect.io/what-is/cve-2018-8581) (Microsoft Exchange Server Privilege Escalation Vulnerability): 2010, 2013, 2016, 2019
- [CVE-2021-33766](https://www.edgeprotect.io/what-is/cve-2021-33766) (Microsoft Exchange Server Information Disclosure): 2013-cumulative_update_23, 2016-cumulative_update_19, 2016-cumulative_update_20, 2019-cumulative_update_8, 2019-cumulative_update_9
- [CVE-2021-42321](https://www.edgeprotect.io/what-is/cve-2021-42321) (Microsoft Exchange Server Remote Code Execution Vulnerability): 2016-cumulative_update_21, 2016-cumulative_update_22, 2019-cumulative_update_10, 2019-cumulative_update_11
- [CVE-2021-34473](https://www.edgeprotect.io/what-is/cve-2021-34473) (Microsoft Exchange Server Remote Code Execution Vulnerability): 2013-cumulative_update_23, 2016-cumulative_update_19, 2016-cumulative_update_20, 2019-cumulative_update_8, 2019-cumulative_update_9
- [CVE-2021-34523](https://www.edgeprotect.io/what-is/cve-2021-34523) (Microsoft Exchange Server Privilege Escalation Vulnerability): 2013-cumulative_update_23, 2016-cumulative_update_19, 2016-cumulative_update_20, 2019-cumulative_update_8, 2019-cumulative_update_9
- [CVE-2021-26858](https://www.edgeprotect.io/what-is/cve-2021-26858) (Microsoft Exchange Server Remote Code Execution Vulnerability): 2010-sp3, 2013-cumulative_update_22, 2013-cumulative_update_23, 2013-sp1, 2016-cumulative_update_8, 2016-cumulative_update_9, 2016-cumulative_update_10, 2016-cumulative_update_11, 2016-cumulative_update_12, 2016-cumulative_update_13, 2016-cumulative_update_14, 2016-cumulative_update_15, 2016-cumulative_update_16, 2016-cumulative_update_17, 2016-cumulative_update_18, 2016-cumulative_update_19, 2019, 2019-cumulative_update_1, 2019-cumulative_update_2, 2019-cumulative_update_3, 2019-cumulative_update_4, 2019-cumulative_update_5, 2019-cumulative_update_6, 2019-cumulative_update_7, 2019-cumulative_update_8
- [CVE-2021-26857](https://www.edgeprotect.io/what-is/cve-2021-26857) (Microsoft Exchange Server Remote Code Execution Vulnerability): 2010-sp3, 2013-cumulative_update_22, 2013-cumulative_update_23, 2013-sp1, 2016-cumulative_update_8, 2016-cumulative_update_9, 2016-cumulative_update_10, 2016-cumulative_update_11, 2016-cumulative_update_12, 2016-cumulative_update_13, 2016-cumulative_update_14, 2016-cumulative_update_15, 2016-cumulative_update_16, 2016-cumulative_update_17, 2016-cumulative_update_18, 2016-cumulative_update_19, 2019, 2019-cumulative_update_1, 2019-cumulative_update_2, 2019-cumulative_update_3, 2019-cumulative_update_4, 2019-cumulative_update_5, 2019-cumulative_update_6, 2019-cumulative_update_7, 2019-cumulative_update_8
- [CVE-2021-26855](https://www.edgeprotect.io/what-is/cve-2021-26855) (Microsoft Exchange Server Remote Code Execution Vulnerability): 2013-cumulative_update_21, 2013-cumulative_update_22, 2013-cumulative_update_23, 2016-cumulative_update_8, 2016-cumulative_update_9, 2016-cumulative_update_10, 2016-cumulative_update_11, 2016-cumulative_update_12, 2016-cumulative_update_13, 2016-cumulative_update_14, 2016-cumulative_update_15, 2016-cumulative_update_16, 2016-cumulative_update_17, 2016-cumulative_update_18, 2016-cumulative_update_19, 2019, 2019-cumulative_update_1, 2019-cumulative_update_2, 2019-cumulative_update_3, 2019-cumulative_update_4, 2019-cumulative_update_5, 2019-cumulative_update_6, 2019-cumulative_update_7, 2019-cumulative_update_8
- [CVE-2020-17144](https://www.edgeprotect.io/what-is/cve-2020-17144) (Microsoft Exchange Server Remote Code Execution Vulnerability): 2010-sp3_rollup_31
- [CVE-2021-27065](https://www.edgeprotect.io/what-is/cve-2021-27065) (Microsoft Exchange Server Remote Code Execution Vulnerability): 2013-cumulative_update_21, 2013-sp1, 2016-cumulative_update_8, 2016-cumulative_update_10, 2016-cumulative_update_11, 2016-cumulative_update_12, 2016-cumulative_update_13, 2016-cumulative_update_14, 2016-cumulative_update_15, 2016-cumulative_update_16, 2016-cumulative_update_17, 2016-cumulative_update_18, 2016-cumulative_update_19, 2019, 2019-cumulative_update_1, 2019-cumulative_update_2, 2019-cumulative_update_3, 2019-cumulative_update_4, 2019-cumulative_update_5, 2019-cumulative_update_6, 2019-cumulative_update_7, 2019-cumulative_update_8
- [CVE-2020-0688](https://www.edgeprotect.io/what-is/cve-2020-0688) (Microsoft Exchange Server Validation Key Remote Code Execution Vulnerability): 2010-sp3_rollup_30, 2013-cumulative_update_23, 2016-cumulative_update_14, 2016-cumulative_update_15, 2019-cumulative_update_3, 2019-cumulative_update_4
- [CVE-2021-31207](https://www.edgeprotect.io/what-is/cve-2021-31207) (Microsoft Exchange Server Security Feature Bypass Vulnerability): 2013-cumulative_update_23, 2016-cumulative_update_19, 2016-cumulative_update_20, 2019-cumulative_update_8, 2019-cumulative_update_9

## Which Exchange Server vulnerabilities are being exploited?

19 flaws are on the government list of vulnerabilities known to be exploited, newest first:

- [CVE-2023-21529](https://www.edgeprotect.io/what-is/cve-2023-21529): Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability. High, CVSS 8.8, chance of use in 30 days 59%, known exploited since 13 April 2026.
- [CVE-2021-31196](https://www.edgeprotect.io/what-is/cve-2021-31196): Microsoft Exchange Server Information Disclosure Vulnerability. High, CVSS 7.2, chance of use in 30 days 54%, known exploited since 21 August 2024.
- [CVE-2024-21410](https://www.edgeprotect.io/what-is/cve-2024-21410): Microsoft Exchange Server Privilege Escalation Vulnerability. Critical, CVSS 9.8, chance of use in 30 days 13%, known exploited since 15 February 2024.
- [CVE-2022-41080](https://www.edgeprotect.io/what-is/cve-2022-41080): Microsoft Exchange Server Privilege Escalation Vulnerability. High, CVSS 8.8, chance of use in 30 days 77%, known exploited since 10 January 2023.
- [CVE-2022-41040](https://www.edgeprotect.io/what-is/cve-2022-41040): Microsoft Exchange Server Server-Side Request Forgery Vulnerability. High, CVSS 8.8, chance of use in 30 days >99%, known exploited since 30 September 2022.
- [CVE-2022-41082](https://www.edgeprotect.io/what-is/cve-2022-41082): Microsoft Exchange Server Remote Code Execution Vulnerability. High, CVSS 8.0, chance of use in 30 days >99%, known exploited since 30 September 2022.
- [CVE-2017-8540](https://www.edgeprotect.io/what-is/cve-2017-8540): Microsoft Malware Protection Engine Improper Restriction of Operations Vulnerability. High, CVSS 7.8, chance of use in 30 days 72%, known exploited since 3 March 2022.
- [CVE-2018-8581](https://www.edgeprotect.io/what-is/cve-2018-8581): Microsoft Exchange Server Privilege Escalation Vulnerability. High, CVSS 7.4, chance of use in 30 days 27%, known exploited since 3 March 2022.
- [CVE-2021-33766](https://www.edgeprotect.io/what-is/cve-2021-33766): Microsoft Exchange Server Information Disclosure. High, CVSS 7.3, chance of use in 30 days 98%, known exploited since 18 January 2022.
- [CVE-2021-42321](https://www.edgeprotect.io/what-is/cve-2021-42321): Microsoft Exchange Server Remote Code Execution Vulnerability. High, CVSS 8.8, chance of use in 30 days 92%, known exploited since 17 November 2021.
- [CVE-2021-34473](https://www.edgeprotect.io/what-is/cve-2021-34473): Microsoft Exchange Server Remote Code Execution Vulnerability. Critical, CVSS 9.1, chance of use in 30 days >99%, known exploited since 3 November 2021.
- [CVE-2021-34523](https://www.edgeprotect.io/what-is/cve-2021-34523): Microsoft Exchange Server Privilege Escalation Vulnerability. Critical, CVSS 9.0, chance of use in 30 days >99%, known exploited since 3 November 2021.
- [CVE-2021-26858](https://www.edgeprotect.io/what-is/cve-2021-26858): Microsoft Exchange Server Remote Code Execution Vulnerability. High, CVSS 7.8, chance of use in 30 days 94%, known exploited since 3 November 2021.
- [CVE-2021-26857](https://www.edgeprotect.io/what-is/cve-2021-26857): Microsoft Exchange Server Remote Code Execution Vulnerability. High, CVSS 7.8, chance of use in 30 days 96%, known exploited since 3 November 2021.
- [CVE-2021-26855](https://www.edgeprotect.io/what-is/cve-2021-26855): Microsoft Exchange Server Remote Code Execution Vulnerability. Critical, CVSS 9.1, chance of use in 30 days >99%, known exploited since 3 November 2021.
- [CVE-2020-17144](https://www.edgeprotect.io/what-is/cve-2020-17144): Microsoft Exchange Server Remote Code Execution Vulnerability. High, CVSS 8.4, chance of use in 30 days 37%, known exploited since 3 November 2021.
- [CVE-2021-27065](https://www.edgeprotect.io/what-is/cve-2021-27065): Microsoft Exchange Server Remote Code Execution Vulnerability. High, CVSS 7.8, chance of use in 30 days >99%, known exploited since 3 November 2021.
- [CVE-2020-0688](https://www.edgeprotect.io/what-is/cve-2020-0688): Microsoft Exchange Server Validation Key Remote Code Execution Vulnerability. High, CVSS 8.8, chance of use in 30 days >99%, known exploited since 3 November 2021.
- [CVE-2021-31207](https://www.edgeprotect.io/what-is/cve-2021-31207): Microsoft Exchange Server Security Feature Bypass Vulnerability. Medium, CVSS 6.6, chance of use in 30 days >99%, known exploited since 3 November 2021.

## Which Exchange Server flaws are most likely to be used?

Ranked by the latest exploit-likelihood forecast (the chance each flaw is used in an attack in the next 30 days):

- [CVE-2021-34473](https://www.edgeprotect.io/what-is/cve-2021-34473): >99%, Critical (CVSS 9.1), known exploited
- [CVE-2021-26855](https://www.edgeprotect.io/what-is/cve-2021-26855): >99%, Critical (CVSS 9.1), known exploited
- [CVE-2021-34523](https://www.edgeprotect.io/what-is/cve-2021-34523): >99%, Critical (CVSS 9.0), known exploited
- [CVE-2022-41082](https://www.edgeprotect.io/what-is/cve-2022-41082): >99%, High (CVSS 8.0), known exploited
- [CVE-2020-0688](https://www.edgeprotect.io/what-is/cve-2020-0688): >99%, High (CVSS 8.8), known exploited
- [CVE-2022-41040](https://www.edgeprotect.io/what-is/cve-2022-41040): >99%, High (CVSS 8.8), known exploited
- [CVE-2021-27065](https://www.edgeprotect.io/what-is/cve-2021-27065): >99%, High (CVSS 7.8), known exploited
- [CVE-2021-31207](https://www.edgeprotect.io/what-is/cve-2021-31207): >99%, Medium (CVSS 6.6), known exploited
- [CVE-2021-33766](https://www.edgeprotect.io/what-is/cve-2021-33766): 98%, High (CVSS 7.3), known exploited
- [CVE-2021-26857](https://www.edgeprotect.io/what-is/cve-2021-26857): 96%, High (CVSS 7.8), known exploited

## Questions

### How many vulnerabilities does Exchange Server have?

We track 232 published vulnerabilities listed under the name Exchange Server, across 10 versions. The most recent Exchange Server flaw added to the known-exploited list is CVE-2023-21529, on 13 April 2026.

### Which Exchange Server vulnerabilities are being exploited?

19 are on the list of flaws known to be exploited. The most recently added are CVE-2023-21529, CVE-2021-31196 and CVE-2024-21410.

### Which versions of Exchange Server do the exploited flaws affect?

Each flaw names its own versions, usually as ranges. The newest, CVE-2023-21529, affects 2013-cumulative_update_23, 2016-cumulative_update_23, 2019-cumulative_update_11, 2019-cumulative_update_12. The versions for every exploited flaw are listed on this page.

### How do I get alerts for Exchange Server?

Create a EdgeProtect account and track Exchange Server. We match it against every published flaw, give each one a risk score from 0 to 100 and keep watching, so you hear about new ones as soon as we know, by email, in the app or by webhook.

## Running Exchange Server?

EdgeProtect keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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