What is the CVSS score of CVE-2026-21520?

CVE-2026-21520 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.1%.

How to fix or mitigate CVE-2026-21520?

Within 24 hours: Audit access logs for Copilot Studio to identify potential unauthorized access; document all sensitive data stored in the platform. Within 7 days: Implement network segmentation to restrict Copilot Studio access to authorized users only; disable public or unauthenticated access if possible. Within 30 days: Develop and execute a data inventory and classification plan; establish continuous monitoring for suspicious access patterns; prepare incident response procedures specific to this vulnerability.

Copilot Studio CVE-2026-21520

HIGH

Command Injection (CWE-77)

2026-01-22 secure@microsoft.com

Command Injection Microsoft AI / ML Copilot Studio

7.5

CVSS 3.1 · NVD

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Send unauthenticated network request
Exploit

Access Copilot Studio endpoint without credentials
Impact

Retrieve sensitive information via exposed API

Vulnerability Assessment

Weakness	CWE CWE-77 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V1 - Encoding and Sanitization Command injection prevention MITRE ATT&CK 1 technique across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Exploitation Conditions	No special conditions — remote unauthenticated exploitation against default Copilot Studio configurations allowing network access to information disclosure endpoints.
Impact	CVSS 7.5 (HIGH). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. Exploitation no authentication required. Exploitable via remote/network.
Exploit ScenarioDerived	A remote attacker without authentication could exploit this vulnerability to compromise the affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Unauthenticated attackers can remotely access sensitive information in Microsoft Copilot Studio due to improper access controls, requiring no authentication or user interaction. This network-based vulnerability exposes confidential data to unauthorized disclosure with no patch currently available.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 21:54 CVSS 7.5

Exposure of Sensitive Information to an Unauthorized Actor in Copilot Studio allows a unauthenticated attacker to view sensitive information through network attack vector [CVSS 7.5 HIGH]

RemediationAI

Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.

Affected Packages

microsoft copilot_studio fix: Microsoft Copilot Studio

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in microsoft

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Classified as CWE-77 (Command Injection). Affects Copilot Studio. Exposure of Sensitive Information to an Unauthorized Actor in Copilot Studio allows a unauthenticated attacker to view sensitive information through network attack vector

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

DescriptionCVE.org

Exposure of Sensitive Information to an Unauthorized Actor in Copilot Studio allows a unauthenticated attacker to view sensitive information through network attack vector

Executive ViewAI

Why It Matters

An unauthenticated attacker can access sensitive information in Copilot Studio without credentials, posing a direct risk to any organization using this platform. Organizations storing confidential data, customer information, or intellectual property in Copilot Studio face potential exposure until this vulnerability is remediated.

Business Impact: High

Compensating Controls

Implement Web Application Firewall (WAF) rules to block unauthenticated requests to sensitive endpoints; restrict network access to Copilot Studio through IP whitelisting and VPN-only access; disable or isolate Copilot Studio if not operationally critical; implement increased logging and monitoring for all access attempts; conduct manual security audits of stored data; consider temporary data removal from Copilot Studio until patch availability is confirmed.

Threat Intelligence Overview

EPSS Score

0.1%

Top 75% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.1%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.