# CVE-2020-16969: Microsoft Exchange Information Disclosure Vulnerability

CVE-2020-16969 is fixed in 5 products on 1 platform, first by KB4581424, released October 13, 2020. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2020-16969
- Priority: High
- CVSS: 7.1 (Important)
- EPSS: 0.0273
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Less Likely
- Published: Oct 13, 2020
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2020-16969

## Description

<p>An information disclosure vulnerability exists in how Microsoft Exchange validates tokens when handling certain messages. An attacker who successfully exploited the vulnerability could use this to gain further information from a user.</p> <p>To exploit the vulnerability, an attacker could include specially crafted OWA messages that could be loaded, without warning or filtering, from the attacker-controlled URL. This callback vector provides an information disclosure tactic used in web beacons and other types of tracking systems.</p> <p>The security update corrects the way that Exchange handles these token validations.</p>

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 |  | [KB4581424](https://patchblox.com/security/data/fix/microsoft/kb4581424.md) | Oct 13, 2020 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 17 |  | [KB4581424](https://patchblox.com/security/data/fix/microsoft/kb4581424.md) | Oct 13, 2020 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 18 |  | [KB4581424](https://patchblox.com/security/data/fix/microsoft/kb4581424.md) | Oct 13, 2020 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 6 |  | [KB4581424](https://patchblox.com/security/data/fix/microsoft/kb4581424.md) | Oct 13, 2020 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 7 |  | [KB4581424](https://patchblox.com/security/data/fix/microsoft/kb4581424.md) | Oct 13, 2020 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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