EUVD-2026-38091
GHSA-vwmm-7w98-r7p2
Severity by source
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Network-reachable Copilot endpoint with no attacker auth (PR:N) but mandatory victim click (UI:R); redirect-to-token-theft chain credibly yields full CIA impact on the tenant account.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Url redirection to untrusted site ('open redirect') in Microsoft 365 Copilot's Business Chat allows an unauthorized attacker to elevate privileges over a network.
AnalysisAI
Privilege elevation in Microsoft 365 Copilot's Business Chat is possible when an attacker abuses an open redirect (CWE-601) to coerce a victim into following a crafted link that lands on an attacker-controlled site. With a CVSS 3.1 base score of 8.8 and high impact across confidentiality, integrity, and availability, successful exploitation lets an unauthorized remote attacker elevate privileges over the network after user interaction. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the target be a licensed Microsoft 365 Copilot user with access to Business Chat and that the victim click an attacker-supplied link rendered or delivered through that surface (UI:R is mandatory in the CVSS vector). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H is unusually severe for an open redirect because Microsoft is asserting that the redirect chain yields high impact on confidentiality, integrity, and availability - almost certainly because the post-redirect step leads to token or session theft enabling account takeover within the M365 tenant. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker crafts a Copilot Business Chat prompt or shared artifact that causes Copilot to surface a link routed through the vulnerable Microsoft redirector, then delivers that link to a target via email or Teams. The victim clicks, trusts the Microsoft-branded URL, and is silently redirected to an attacker-controlled site that mimics the Microsoft 365 sign-in flow or triggers an OAuth consent prompt, yielding session tokens that the attacker replays to elevate privileges within the tenant. … |
| Remediation | Patch available per vendor advisory - because Microsoft 365 Copilot Business Chat is a cloud service, Microsoft deploys the fix server-side and tenants do not need to install an update; administrators should confirm remediation status against the MSRC entry at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-47645. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Inventory all users and teams with Microsoft 365 Copilot Business Chat access; document business-critical use cases and data flows. …
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