# CVE-2016-3366: Microsoft Outlook Spoofing Vulnerability

CVE-2016-3366 is fixed in 9 products on 1 platform, first by KB3118303, released September 13, 2016. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2016-3366
- Priority: High
- CVSS: n/a (Important)
- EPSS: 0.1623
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Unlikely
- Published: Sep 13, 2016
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2016-3366

## Description

<p>A spoofing vulnerability exists when Microsoft Outlook does not strictly adhere to RFC2046, and improperly identifies the end of a MIME attachment. An improper MIME attachment ending may cause antivirus or antispam scanning to not work as intended.</p> <p>To exploit the vulnerability, an attacker could send a specially crafted email attachment to a user in an attempt to launch a social engineering attack, such as phishing.</p> <p>The security update addresses the vulnerability by correcting how Outlook determines the end of MIME messages.</p>

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Microsoft Outlook 2007 Service Pack 3 |  | [KB3118303](https://patchblox.com/security/data/fix/microsoft/kb3118303.md) | Sep 13, 2016 |
| Microsoft | Microsoft Outlook 2010 Service Pack 2 (32-bit editions) |  | [KB3118313](https://patchblox.com/security/data/fix/microsoft/kb3118313.md) | Sep 13, 2016 |
| Microsoft | Microsoft Outlook 2010 Service Pack 2 (64-bit editions) |  | [KB3118313](https://patchblox.com/security/data/fix/microsoft/kb3118313.md) | Sep 13, 2016 |
| Microsoft | Microsoft Outlook 2013 RT Service Pack 1 |  | [KB3118280](https://patchblox.com/security/data/fix/microsoft/kb3118280.md) | Sep 13, 2016 |
| Microsoft | Microsoft Outlook 2013 Service Pack 1 (32-bit editions) |  | [KB3118280](https://patchblox.com/security/data/fix/microsoft/kb3118280.md) | Sep 13, 2016 |
| Microsoft | Microsoft Outlook 2013 Service Pack 1 (64-bit editions) |  | [KB3118280](https://patchblox.com/security/data/fix/microsoft/kb3118280.md) | Sep 13, 2016 |
| Microsoft | Microsoft Outlook 2016 (32-bit edition) |  | [KB3118293](https://patchblox.com/security/data/fix/microsoft/kb3118293.md) | Sep 13, 2016 |
| Microsoft | Microsoft Outlook 2016 (64-bit edition) |  | [KB3118293](https://patchblox.com/security/data/fix/microsoft/kb3118293.md) | Sep 13, 2016 |
| Microsoft | Microsoft Outlook 2016 for Mac |  | [KB3186807](https://patchblox.com/security/data/fix/microsoft/kb3186807.md) | Sep 13, 2016 |

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Data as of 2026-11-07T06:34:28Z 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