CVE-2026-66301 Overview
CVE-2026-66301 is an information disclosure vulnerability in Microsoft Dynamics 365 (on-premises). An authenticated attacker can exploit the flaw over a network to read sensitive information that should be restricted to authorized users. The weakness is categorized as [CWE-200] Exposure of Sensitive Information to an Unauthorized Actor.
The vulnerability requires low privileges and no user interaction, which lowers the barrier for exploitation inside environments where any authenticated foothold exists. Microsoft published details in the Microsoft Security Response Center advisory.
Critical Impact
An authenticated network attacker can read confidential business records, personally identifiable information, or configuration data stored in Microsoft Dynamics 365 (on-premises) without altering data or degrading availability.
Affected Products
- Microsoft Dynamics 365 (on-premises)
Discovery Timeline
- 2026-08-11 - CVE-2026-66301 published to NVD
- 2026-08-11 - Last updated in NVD database
Technical Details for CVE-2026-66301
Vulnerability Analysis
CVE-2026-66301 exposes sensitive information handled by Microsoft Dynamics 365 (on-premises) to authenticated users who should not have access to it. The confidentiality impact is high, while integrity and availability remain unaffected. An attacker with valid low-privilege credentials can query the application over the network and retrieve data outside their authorization scope.
Because Dynamics 365 stores customer relationship management (CRM) records, financial data, and business workflows, the exposed information can support downstream attacks. Disclosed data can enable social engineering, targeted phishing, or reconnaissance against connected Microsoft 365 tenants and Active Directory environments.
Root Cause
The underlying weakness maps to [CWE-200]. Dynamics 365 returns sensitive information to a caller that has not been properly authorized to view it. This typically results from missing or incomplete access control checks in an application endpoint, incorrect scoping of a query, or verbose responses that include fields beyond the caller's permission set.
Attack Vector
Exploitation occurs over the network against a reachable Dynamics 365 (on-premises) deployment. The attacker must hold valid credentials but does not need administrative privileges. No user interaction is required. The attacker issues crafted requests to the vulnerable endpoint and receives responses containing data that authorization policy should have withheld.
No public proof-of-concept, exploit code, or reports of exploitation in the wild are listed for CVE-2026-66301. The vulnerability is not present on the CISA Known Exploited Vulnerabilities catalog. Refer to the Microsoft Security Update for CVE-2026-66301 for vendor-supplied technical details.
Detection Methods for CVE-2026-66301
Indicators of Compromise
- Unusual volumes of read or export operations against Dynamics 365 records from a single authenticated account.
- Access to entity records, views, or reports outside a user's assigned business unit or security role.
- Requests to Dynamics 365 web services or OData endpoints returning oversized response payloads.
Detection Strategies
- Audit Dynamics 365 access logs for accounts retrieving records inconsistent with their job role or historical baseline.
- Correlate authentication events with API request patterns to identify low-privilege accounts probing multiple entities.
- Enable Dynamics 365 auditing on sensitive entities and forward events to a centralized log platform for behavioral analysis.
Monitoring Recommendations
- Track outbound data volume from Dynamics 365 application servers for anomalous spikes.
- Alert on repeated authorization failures immediately followed by successful reads on the same entity type.
- Review service account activity for read patterns that deviate from documented integrations.
How to Mitigate CVE-2026-66301
Immediate Actions Required
- Apply the security update referenced in the Microsoft Security Update for CVE-2026-66301 advisory to all affected Dynamics 365 (on-premises) servers.
- Inventory Dynamics 365 (on-premises) deployments and prioritize internet-facing or partner-accessible instances.
- Review recent audit logs for suspicious read activity by low-privilege accounts prior to patching.
Patch Information
Microsoft has published a security update for CVE-2026-66301 through the Microsoft Security Response Center. Administrators should download and deploy the update from the Microsoft Security Update for CVE-2026-66301 guidance page and verify successful installation on every Dynamics 365 (on-premises) role server.
Workarounds
- Restrict network access to Dynamics 365 (on-premises) endpoints using firewalls, VPNs, or reverse-proxy allow-lists until the patch is applied.
- Enforce the principle of least privilege by reviewing security roles, field-level security profiles, and business unit assignments.
- Rotate credentials for accounts that showed anomalous activity and require multi-factor authentication for all Dynamics 365 users.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
