Summary
Impact: Information Disclosure. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
According to the CVSS metric, the attack vector is network (AV:N) and user interaction is required (UI:R). Why does the CVE title indicate that this is information disclosure?
An attacker who successfully exploited this vulnerability could use malicious email to cause Copilot to present authoritative‑looking phishing messages that prompt the user to click links leading to data exfiltration or navigation to a malicious site.
According to the CVSS metrics, successful exploitation of this vulnerability could lead to major loss of confidentiality (C:H), and some loss of integrity (I:L), but no loss of availability (A:N). What does that mean for this vulnerability?
An attacker who successfully exploited this vulnerability could potentially view sensitive information (confidentiality) or make limited changes to disclosed information (integrity); however, it is unlikely that both would be impacted simultaneously, and the attacker would not be able to affect availability.
Security updates
2.106.26020617 — https://apps.apple.com/us/app/microsoft-onenote/id410395246?platform=mac
5.2605 — https://go.microsoft.com/fwlink/p/?linkid=831049
5.2605 — https://learn.microsoft.com/en-us/officeupdates/release-notes-outlook-mobile
2.107.2 — https://apps.apple.com/us/app/microsoft-365-copilot/id541164041
145.3800.99 — https://docs.microsoft.com/en-us/DeployEdge/microsoft-edge-relnotes-security
8.3.1 — https://apps.apple.com/us/app/microsoft-teams/id1113153706
1.0.0.2026043102 — https://play.google.com/store/apps/details?id=com.microsoft.teams
16.0.19822.20038 — https://play.google.com/store/apps/details?id=com.microsoft.office.excel&hl=en_US
16.0.19822.20038 — https://play.google.com/store/apps/details?id=com.microsoft.office.word&hl=en_US
2.106.26020617 — https://apps.apple.com/us/app/microsoft-powerpoint/id586449534?platform=mac
2.106.26020617 — https://apps.apple.com/us/app/microsoft-word/id462054704?mt=12
2.106.26020617 — https://apps.apple.com/us/app/microsoft-loop/id1637682491
5.2605 — https://apps.apple.com/ca/app/microsoft-outlook/id951937596
16.0.19815.10000 — https://play.google.com/store/search?q=copilot+365&c=apps
2.2.260210.21290750 — https://play.google.com/store/search?q=powerbi&c=apps
1.2.260302.2193910 — https://apps.apple.com/us/app/microsoft-power-bi/id929738808
16.0.19725.20142 — https://play.google.com/store/apps/details?id=com.microsoft.office.onenote
16.0.19822.20038 — https://play.google.com/store/apps/details?id=com.microsoft.office.powerpoint&hl=en_US
2.106.26020617 — https://apps.apple.com/us/app/microsoft-excel/id586683407?platform=mac
Vulnerabilities 1
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High 7.1
M365 Copilot Information Disclosure Vulnerability
AI command injection in M365 Copilot allows an unauthorized attacker to disclose information over a network.
Revision history
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#3
Updated CWE value. This is an informational change only.
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#1
Information published.
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#2
Updated an acknowledgement. This is an informational change only.
References
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CVE-2026-26133 M365 Copilot Information Disclosure Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26133
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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