# Improper authentication in Microsoft Exchange Server 2013 and others

CVE record · `CVE-2020-0688`

- **Identifiers:** `CVE-2020-0688`
- **State:** Confirmed
- **Severity:** CVSS 8.8 High
- **Critical:** Yes: KEV, CVSS 7+ and EPSS
- **CNA:** microsoft
- **Weakness (CWE):** [CWE-287](https://cwe.mitre.org/data/definitions/287.html)
- **Tags:** [Authentication bypass](https://agentprime.io/advisories/tag/auth-bypass.md)
- **Technologies:** [Microsoft Exchange Server 2013](https://agentprime.io/advisories/technology/microsoft-exchange-server-2013.md) · [Microsoft Exchange Server 2019 Cumulative Update 3](https://agentprime.io/advisories/technology/microsoft-exchange-server-2019-cumulative-update-3.md) · [Microsoft Exchange Server 2016 Cumulative Update 14](https://agentprime.io/advisories/technology/microsoft-exchange-server-2016-cumulative-update-14.md) · [Microsoft Exchange Server 2016 Cumulative Update 15](https://agentprime.io/advisories/technology/microsoft-exchange-server-2016-cumulative-update-15.md) · [Microsoft Exchange Server 2019 Cumulative Update 4](https://agentprime.io/advisories/technology/microsoft-exchange-server-2019-cumulative-update-4.md) · [Microsoft Exchange Server 2010 Service Pack 3 Update Rollup 30](https://agentprime.io/advisories/technology/microsoft-exchange-server-2010-service-pack-3-update-rollup-30.md)
- **Published:** 11 Feb 2020
- **Updated:** 21 Oct 2025
- **Reviewed by a person:** No

Published by the CVE Program (CNA: microsoft) at 11 Feb 2020, 21:22 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

## Critical

Critical, because:

- In CISA’s KEV catalogue since 3 Nov 2021: it is known to be exploited.
- CVSS score 8.8 (7.0 or more) and EPSS 1.00 (0.1 or more): a high score and a real chance of exploitation in the next 30 days.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected products, as the CNA wrote them

- Vendor: Microsoft. Product: Microsoft Exchange Server 2013.
  - affected: `Cumulative Update 23`
- Vendor: Microsoft. Product: Microsoft Exchange Server 2019 Cumulative Update 3.
  - affected: `unspecified`
- Vendor: Microsoft. Product: Microsoft Exchange Server 2016 Cumulative Update 14.
  - affected: `unspecified`
- Vendor: Microsoft. Product: Microsoft Exchange Server 2016 Cumulative Update 15.
  - affected: `unspecified`
- Vendor: Microsoft. Product: Microsoft Exchange Server 2019 Cumulative Update 4.
  - affected: `unspecified`
- Vendor: Microsoft. Product: Microsoft Exchange Server 2010 Service Pack 3 Update Rollup 30.
  - affected: `unspecified`

## Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

## Severity and exploitation

- 8.8 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`, from ADP (CISA-ADP)

- **CISA KEV:** Listed since 3 Nov 2021: known to be exploited. CISA reports use in ransomware campaigns.
- **EPSS:** 1.00, the 99th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the CVE Program, published 11 Feb 2020. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2020-0688](https://www.cve.org/CVERecord?id=CVE-2020-0688)
- [NVD: CVE-2020-0688](https://nvd.nist.gov/vuln/detail/CVE-2020-0688)

### References from the CNA

- <https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0688>
- <https://www.zerodayinitiative.com/advisories/ZDI-20-258/>
- <http://packetstormsecurity.com/files/156592/Microsoft-Exchange-2019-15.2.221.12-Remote-Code-Execution.html>
- <http://packetstormsecurity.com/files/156620/Exchange-Control-Panel-Viewstate-Deserialization.html>

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.

## Check whether this affects you

This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it. Compare the affected versions above with what you run.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), `get_advisory` returns this record and `search_advisories` finds related ones. Setup: <https://agentprime.io/mcp.md>
- As JSON: <https://api.agentprime.io/v1/advisories/CVE-2020-0688>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2020-0688/>. Everything for agents: <https://agentprime.io/llms.txt>.