EUVD-2026-48457
GHSA-cfm3-7vpc-px47
Severity by source
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Network-reachable RCE needing only a low-privilege authenticated identity (PR:L), no user interaction, with a cloud service scope change (S:C) and full CIA impact.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Deserialization of untrusted data in M365 Copilot allows an authorized attacker to execute code over a network.
AnalysisAI
Remote code execution in Microsoft 365 Copilot allows an authenticated attacker to run arbitrary code over the network by supplying maliciously crafted serialized data (CWE-502). The flaw carries a CVSS 9.9 rating driven by a scope change and full confidentiality, integrity, and availability impact, and because Copilot is a Microsoft-hosted cloud service, exploitation would affect the shared multi-tenant platform. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires an authenticated foothold: the CVSS vector specifies PR:L, so the attacker must hold low-level privileges (a valid authenticated identity/session with Microsoft 365 Copilot), consistent with the description's 'authorized attacker.' No user interaction is needed (UI:N) and the attack is network-based (AV:N) with low complexity (AC:L). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The signals are largely consistent in pointing to a serious flaw but with an important caveat. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who holds valid low-privilege credentials within a tenant submits crafted serialized data through a Copilot-facing input or connected data channel; when Copilot deserializes it, an object gadget chain triggers arbitrary code execution across the service scope boundary. No public exploit code is known to exist (exploit maturity Unproven), and no user interaction is required, so the primary barrier is obtaining authenticated access to the service. |
| Remediation | Patch available per vendor advisory: Microsoft has released a fix, and because Microsoft 365 Copilot is a Microsoft-hosted cloud service the remediation is applied server-side by Microsoft, so no customer-installed update is typically required - verify remediation status and any required tenant actions via the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50517. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Microsoft 365 Copilot users and business-critical integrations in the organization, assess dependencies and risk exposure, and prepare a patch test environment. …
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Same weakness CWE-502 – Deserialization of Untrusted Data
View allSame technique Deserialization
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External POC / Exploit Code
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