# CVE-2017-8621: Microsoft Exchange Open Redirect Vulnerability

CVE-2017-8621 is fixed in 4 products on 1 platform, first by KB4018588, released July 11, 2017. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2017-8621
- Priority: Routine
- CVSS: n/a (Moderate)
- EPSS: 0.0317
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Unlikely
- Published: Jul 11, 2017
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2017-8621

## Description

<p>An open redirect vulnerability exists in Microsoft Exchange that could lead to spoofing.</p> <p>To exploit the vulnerability, an attacker could send a link that has a specially crafted URL, and convince the user to click the link. When an authenticated Exchange user clicks the link, the authenticated user's browser session could be redirected to a malicious site that is designed to impersonate a legitimate website. By doing so, the attacker could trick the user and potentially acquire sensitive information, such as the user's credentials.</p> <p>The update addresses the vulnerability by correcting how Exchange handles open redirect requests.</p>

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Microsoft Exchange Server 2010 Service Pack 3 |  | [KB4018588](https://patchblox.com/security/data/fix/microsoft/kb4018588.md) | Jul 11, 2017 |
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 16 |  | [KB4018588](https://patchblox.com/security/data/fix/microsoft/kb4018588.md) | Jul 11, 2017 |
| Microsoft | Microsoft Exchange Server 2013 Service Pack 1 |  | [KB4018588](https://patchblox.com/security/data/fix/microsoft/kb4018588.md) | Jul 11, 2017 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 5 |  | [KB4018588](https://patchblox.com/security/data/fix/microsoft/kb4018588.md) | Jul 11, 2017 |

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Data as of 2026-11-07T12:40:37Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo