CVE-2024-38194: Azure Web Apps Privilege Escalation Flaw

CVE-2024-38194 Overview

CVE-2024-38194 is an improper authorization vulnerability in Microsoft Azure Web Apps. An authenticated attacker can exploit the flaw over a network to elevate privileges within the affected service. Microsoft assigned a CVSS 3.1 score of 9.9 and classified the issue as Critical. The weakness is categorized under [CWE-20] Improper Input Validation. The vulnerability does not require user interaction and has a scope change, meaning successful exploitation impacts resources beyond the initially vulnerable component. No public proof-of-concept code or in-the-wild exploitation has been confirmed.

Critical Impact

Authenticated attackers can elevate privileges across tenant boundaries in Azure Web Apps, gaining high-impact access to confidentiality, integrity, and availability of affected resources.

Affected Products

• Microsoft Azure Web Apps (cloud service)
• Applications deployed on the Azure App Service Web Apps platform
• Workloads sharing multi-tenant Azure Web Apps infrastructure

Discovery Timeline

• 2024-09-10 - CVE-2024-38194 published to NVD
• 2024-09-17 - Last updated in NVD database

Technical Details for CVE-2024-38194

Vulnerability Analysis

The vulnerability resides in the authorization logic of Microsoft Azure Web Apps, a managed Platform-as-a-Service (PaaS) offering for hosting web applications. An authenticated principal with low privileges can bypass authorization checks to perform actions reserved for higher-privileged roles. The scope change indicates that exploitation can cross security boundaries between the authenticated identity and other resources or tenants managed by the Web Apps service.

Root Cause

Microsoft attributes the issue to improper authorization, mapped to [CWE-20]. The service did not consistently validate that an authenticated request was authorized to access the targeted resource or operation. As a managed cloud service, the defect was remediated by Microsoft within the Azure platform, and no customer-side patching is required.

Attack Vector

An attacker must hold valid credentials to interact with Azure Web Apps over the network. Once authenticated, the attacker issues crafted requests that exercise the affected control path. Because authorization is not properly enforced, the request executes with elevated privileges. The low attack complexity and lack of user interaction make exploitation reliable for any actor with baseline access. EPSS data places this CVE in the upper quartile of likelihood among recent vulnerabilities.

No verified exploitation code is publicly available. Refer to the Microsoft Security Update CVE-2024-38194 advisory for service-specific technical details.

Detection Methods for CVE-2024-38194

Indicators of Compromise

• Unexpected privilege changes or role assignments on Azure Web Apps resources
• Management plane operations performed by identities that historically lack those permissions
• Anomalous Azure Resource Manager (ARM) API calls targeting Web Apps configuration or deployment endpoints

Detection Strategies

• Review Azure Activity Logs and Microsoft Entra ID audit logs for authorization decisions on Web Apps resources that deviate from established baselines
• Correlate sign-in events with subsequent privileged actions to identify low-privileged accounts performing high-impact operations
• Hunt for service principals or users invoking Web Apps administrative APIs outside expected automation pipelines

Monitoring Recommendations

• Stream Azure Activity Logs, Microsoft Entra ID logs, and App Service diagnostic logs to a centralized analytics platform
• Alert on changes to publishing credentials, deployment slots, and app settings made by non-standard identities
• Track new role assignments scoped to Web Apps subscriptions or resource groups

How to Mitigate CVE-2024-38194

Immediate Actions Required

• Confirm Microsoft has remediated the vulnerability in your tenant by reviewing the Microsoft Security Update CVE-2024-38194 advisory
• Audit Azure role-based access control (RBAC) assignments on Web Apps and remove unnecessary privileges
• Rotate publishing profiles, deployment credentials, and managed identity secrets associated with Azure Web Apps
• Review recent Activity Log entries for suspicious privilege escalations

Patch Information

Azure Web Apps is a Microsoft-managed service. Microsoft addressed the vulnerability within the Azure platform, and no customer-side update is required. Customers should verify advisory status through the Microsoft Security Update CVE-2024-38194 page.

Workarounds

• Enforce least privilege on all Azure RBAC role assignments for Web Apps resources
• Require multi-factor authentication and Conditional Access policies for any identity that can access Azure management APIs
• Restrict management plane access to specific networks or Privileged Identity Management (PIM) just-in-time activations
• Disable basic authentication for SCM and FTP endpoints on App Service where feasible

# Configuration example: enforce least privilege and disable basic auth on App Service
az role assignment list --scope /subscriptions/<sub-id>/resourceGroups/<rg>/providers/Microsoft.Web/sites/<app> --output table

az resource update \
  --resource-group <rg> \
  --name scm \
  --namespace Microsoft.Web \
  --resource-type basicPublishingCredentialsPolicies \
  --parent sites/<app> \
  --set properties.allow=false

az resource update \
  --resource-group <rg> \
  --name ftp \
  --namespace Microsoft.Web \
  --resource-type basicPublishingCredentialsPolicies \
  --parent sites/<app> \
  --set properties.allow=false