External risk intelligence

Microsoft 365 Copilot Chat Command Injection Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2025-59286

Microsoft 365 Copilot is a web-based, cloud-delivered service. It is designed as an internet-facing application that users access to interact with organizational data via chat interfaces. Because it is a web-based tool commonly deployed and accessed via public internet infrastructure as part of an organization's standard collaboration platform, it presents a likely attack surface for remote access.

Command Injection

Microsoft 365 Copilot Chat

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory details a critical vulnerability affecting Microsoft 365 Copilot chat. The issue involves improper handling of commands, which could allow an attacker to potentially access sensitive information over a network. While the direct business impact requires further assessment, understanding the nature of this vulnerability is important for maintaining data security.

Attackers may reveal information through this flaw.
Key for leaders to understand potential data exposure risks.
Confirm relevance and assess your exposure level.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted commands over a network to the Copilot chat feature. This could allow them to gain unauthorized access to sensitive information and potentially make minor modifications to data.

No privileges or user interaction needed.
Triggered by sending malicious commands.
Risk of unauthorized information disclosure.

Live Threat

Current exploitation, exposure, and threat context

An improper handling of commands within Microsoft 365 Copilot could allow an unauthenticated attacker to reveal sensitive information over a network. This vulnerability occurs when specific commands are not neutralized correctly, potentially leading to unauthorized data disclosure when supported by the advisory.

Network-accessible service information.
Through crafted commands.
Disclosure of sensitive data.

Operational Fix

Recommended remediation, mitigation, and detection steps

The command injection vulnerability in Microsoft 365 Copilot necessitates immediate attention from teams responsible for cloud-based application security and platform management. The first practical step is to identify all instances of Microsoft 365 Copilot within the environment, assess their exposure to the network, and determine their business criticality. Once identified and prioritized, the accountable owner should be confirmed to initiate a coordinated remediation plan.

Cloud platform and application security teams own this.
Verify Copilot accessibility and business impact.
Plan and coordinate remediation efforts.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Microsoft 365 Copilot Chat?

Microsoft 365 Copilot Chat is a cloud-based artificial intelligence assistant integrated into the Microsoft 365 productivity suite. It functions as a conversational interface that allows users to query, summarize, and interact with organizational data across applications like email, documents, and calendars to improve workflow efficiency.

What does CVE-2025-59286 mean for data security?

This vulnerability is classified as CWE-77, or command injection. It occurs when an application fails to properly clean input, allowing an attacker to inject their own commands. In the context of this CVE, this flaw could be leveraged to bypass security controls and gain unauthorized access to sensitive information that the system is intended to protect.

How can an attacker trigger this vulnerability?

An attacker triggers this bug by sending specially crafted commands over a network to the Copilot interface. Because this is a command injection flaw, it does not require the attacker to have pre-existing privileges or rely on a user to click a link. However, the system is not susceptible to commands that are properly neutralized by the application's underlying security logic.

Is my organization at risk from this vulnerability?

Halo Surface Signal indicates that Microsoft 365 Copilot is a web-based, cloud-delivered service, making it inherently internet-facing. Because organizations access this platform via public internet infrastructure, the service is generally considered to have an external attack surface, which is a primary factor in determining if you should prioritize this issue.

What should I do first to address this security flaw?

Begin by identifying all areas where Microsoft 365 Copilot is deployed across your organization. Once you have an inventory, assess the business criticality of those specific implementations. After evaluating how your teams use the tool, coordinate with the appropriate cloud platform owners to establish a remediation plan and monitor for official guidance on updates.

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2025-59286

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.