CVE-2026-50517Network attack vector

Authenticated code execution via untrusted deserialization

Published Jul 24, 2026 · Updated Jul 24, 2026

Deserialization of untrusted data in Microsoft 365 Copilot allows remote authenticated users to execute code over a network. Microsoft has not disclosed the serialized input, processing component, or operation that instantiates attacker-controlled data. Exploitation requires a signed-in account and can compromise data and service operation within the hosted service's security context.

CVSS severity9.9
Critical
EPSS probability1.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deserialization of untrusted data in Microsoft 365 Copilot allows remote authenticated users to execute code over a network. Microsoft has not disclosed the serialized input, processing component, or operation that instantiates attacker-controlled data. Exploitation requires a signed-in account and can compromise data and service operation within the hosted service's security context.

The record

CVE
CVE-2026-50517
Published
Jul 24, 2026
Updated
Jul 24, 2026
Vendor
Microsoft
Product
Microsoft 365 Copilot
Classifications
CWE-502, CAPEC-586, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=-

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft 365 Copilotversion=-

Published CVSS scores

9.9Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
CAPEC-586Object Injection
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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