# CVE-2017-11761: Microsoft Exchange Information Disclosure Vulnerability

CVE-2017-11761 is fixed in 4 products on 1 platform, first by KB4045655, released December 12, 2017. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2017-11761
- Priority: High
- CVSS: n/a (Important)
- EPSS: 0.0656
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Unlikely
- Published: Sep 12, 2017
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2017-11761

## Description

<p>An input sanitization issue exists with Microsoft Exchange that could potentially result in unintended Information Disclosure. An attacker who successfully exploited the vulnerability could identify the existence of RFC1918 addresses on the local network from a client on the Internet. An attacker could use this internal host information as part of a larger attack.</p> <p>To exploit the vulnerability, an attacker could include specially crafted tags in Calendar-related messages sent to an Exchange server. These specially-tagged messages could prompt the Exchange server to fetch information from internal servers. By observing telemetry from these requests, a client could discern properties of internal hosts intended to be hidden from the Internet.</p> <p>The update corrects the way that Exchange parses Calendar-related messages.</p>

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 17 |  | [KB4045655](https://patchblox.com/security/data/fix/microsoft/kb4045655.md) | Dec 12, 2017 |
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 18 |  | [KB4045655](https://patchblox.com/security/data/fix/microsoft/kb4045655.md) | Dec 12, 2017 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 6 |  | [KB4045655](https://patchblox.com/security/data/fix/microsoft/kb4045655.md) | Dec 12, 2017 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 7 |  | [KB4045655](https://patchblox.com/security/data/fix/microsoft/kb4045655.md) | Dec 12, 2017 |

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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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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