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CVE-2026-80084: Microsoft Office Outlook Information Disclosure Vulnerability

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-08 · updated 2026-10-31
• Weakness: CWE-125

Description

Out-of-bounds read in Microsoft Office Outlook allows an unauthorized attacker to disclose information over a network.

Affected products

• Microsoft 365 Apps: all versions
• Microsoft Office 2016: all versions
• Microsoft Office 2019: all versions
• Microsoft Office 2021: all versions
• Microsoft Office LTSC 2024: all versions
• Microsoft 365 Apps: from 16.0.1 before 16.0.20326.20138 — fixed in 16.0.20326.20138
• Microsoft Office LTSC 2021: from 16.0.1 before 16.0.14334.20906 — fixed in 16.0.14334.20906
• Microsoft Office: from 16.0.0 before 16.0.5569.1002 — fixed in 16.0.5569.1002
• Microsoft Office LTSC 2024: from 16.0.0 before 16.0.17932.20976 — fixed in 16.0.17932.20976

How to fix

Upgrade to a fixed version: Microsoft 365 Apps 16.0.20326.20138; Microsoft Office LTSC 2021 16.0.14334.20906; Microsoft Office 16.0.5569.1002; Microsoft Office LTSC 2024 16.0.17932.20976. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-80084

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