Summary
Impact: Information Disclosure. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?
An attacker must send a user a malicious Office file and convince them to open it.
What type of information could be disclosed by this vulnerability?
An attacker who successfully exploited this vulnerability could potentially read small portions of heap memory.
Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.
Security updates
16.0.5561.1001 — https://support.microsoft.com/help/5002891
16.0.5561.1001 — https://support.microsoft.com/help/5002892
16.0.10417.20175 — https://support.microsoft.com/help/5002883
16.0.10417.20175 — https://support.microsoft.com/help/5002885
https — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
16.111.26071215 — https://go.microsoft.com/fwlink/p/?linkid=831049
16.0.19725.20434 — https://support.microsoft.com/help/5002882
16.0.5561.1000 — https://support.microsoft.com/help/5002887
16.111.26071215 — https://www.microsoft.com/en-us/microsoft-365/mac/microsoft-365-for-mac?msockid=35f9adb0e74b61392038b90de6fe608c
Vulnerabilities 1
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Medium 5.5
Microsoft Office Information Disclosure Vulnerability
Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.
Revision history
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#1
Information published.
References
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CVE-2026-55027 Microsoft Office Information Disclosure Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55027
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss