What’s Vulnerable › Vulnerabilities

CVE-2020-16949: Microsoft Outlook Denial of Service Vulnerability

• Severity: medium (CVSS 5.0 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-10-16 · updated 2026-06-17
• Weakness: CWE-401

Description

<p>A denial of service vulnerability exists in Microsoft Outlook software when the software fails to properly handle objects in memory. An attacker who successfully exploited the vulnerability could cause a remote denial of service against a system.</p> <p>Exploitation of the vulnerability requires that a specially crafted email be sent to a vulnerable Outlook server.</p> <p>The security update addresses the vulnerability by correcting how Microsoft Outlook handles objects in memory.</p>

Affected products

• Microsoft 365 Apps: all versions
• Microsoft Office: 2019
• Microsoft Outlook: 2010-sp2, 2013-sp1, 2016
• Microsoft Windows 10 Version 1607: 1607, 1709, 1803, 1809, 1903, 1909 (+1)
• Microsoft Windows 7: all versions
• Microsoft Windows 8.1: all versions
• Microsoft Windows RT 8.1: all versions
• Microsoft Windows Server 2008: r2-sp1
• Microsoft Windows Server 2012: r2
• Microsoft Windows Server 2016: 1903, 1909, 2004
• Microsoft Windows Server 2019: all versions
• Microsoft 365 Apps: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Outlook 2010 Service Pack 2: from 13.0.0.0 before publication — fixed in publication
• Microsoft Outlook 2013 Service Pack 1: from 15.0.0.0 before publication — fixed in publication
• Microsoft Office: from 19.0.0 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Outlook 2016 for Mac: from 16.0.0.0 before publication — fixed in publication

How to fix

Upgrade to a fixed version: Microsoft 365 Apps https://aka.ms/OfficeSecurityReleases; Microsoft Outlook 2010 Service Pack 2 publication; Microsoft Outlook 2013 Service Pack 1 publication; Microsoft Office https://aka.ms/OfficeSecurityReleases; Microsoft Outlook 2016 for Mac publication. Check the vendor advisory for mitigations.

References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-16949
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-16949

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