What’s Vulnerable › Vulnerabilities

CVE-2023-35311: Microsoft Outlook Security Feature Bypass Vulnerability

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2023-07-11
• EPSS: 15.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-07-11 · updated 2026-10-08
• Weakness: CWE-367

Description

Microsoft Outlook Security Feature Bypass Vulnerability

Affected products

• Microsoft 365 Apps: all versions
• Microsoft Office 2019: all versions
• Microsoft Office 2021: all versions
• Microsoft Outlook: 2013, 2013-sp1, 2016
• Microsoft 365 Apps: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Office LTSC 2021: from 16.0.1 before https://aka.ms/OfficeSecurityReleases — fixed in https://aka.ms/OfficeSecurityReleases
• Microsoft Outlook 2013: from 14.0.0 before 15.0.5571.1000 — fixed in 15.0.5571.1000
• Microsoft Outlook 2013 Service Pack 1: from 15.0.0.0 before 15.0.5571.1000 — fixed in 15.0.5571.1000
• 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 16.0.5404.1000 — fixed in 16.0.5404.1000

How to fix

Upgrade to a fixed version: Microsoft 365 Apps https://aka.ms/OfficeSecurityReleases; Microsoft Office LTSC 2021 https://aka.ms/OfficeSecurityReleases; Microsoft Outlook 2013 15.0.5571.1000; Microsoft Outlook 2013 Service Pack 1 15.0.5571.1000; Microsoft Office https://aka.ms/OfficeSecurityReleases; Microsoft Outlook 2016 for Mac 16.0.5404.1000. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-35311
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-35311
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-35311

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