CVE-2025-49752: Azure Bastion Privilege Escalation Flaw

CVE-2025-49752 Overview

CVE-2025-49752 is a critical elevation of privilege vulnerability affecting Microsoft Azure Bastion Developer. This vulnerability allows attackers to escalate privileges within the Azure Bastion service, potentially compromising the integrity and confidentiality of connected cloud resources. The vulnerability is classified under CWE-294 (Authentication Bypass by Capture-replay), indicating that authentication mechanisms may be susceptible to replay attacks that enable unauthorized privilege escalation.

Critical Impact
This vulnerability enables attackers to elevate privileges within Azure Bastion environments, potentially gaining unauthorized access to protected virtual machines and sensitive cloud infrastructure. The changed scope means successful exploitation can impact resources beyond the vulnerable component.

Affected Products

Microsoft Azure Bastion Developer

Discovery Timeline

2025-11-20 - CVE-2025-49752 published to NVD
2025-11-21 - Last updated in NVD database

Technical Details for CVE-2025-49752

Vulnerability Analysis

This elevation of privilege vulnerability in Azure Bastion Developer stems from authentication bypass weaknesses that can be exploited via capture-replay techniques. Azure Bastion is a managed PaaS service that provides secure RDP and SSH access to virtual machines without exposing them to public IP addresses. The vulnerability allows an unauthenticated attacker to bypass normal authentication controls and escalate privileges within the Bastion service context.

The vulnerability has a changed scope, meaning successful exploitation can affect resources beyond the vulnerable Azure Bastion component itself—potentially impacting connected virtual machines and other Azure resources accessible through the Bastion service.

Root Cause

The root cause is classified as CWE-294: Authentication Bypass by Capture-replay. This indicates that the authentication mechanism within Azure Bastion Developer fails to adequately protect against replay attacks. An attacker who captures valid authentication tokens or session data may be able to replay these credentials to gain elevated access without proper authorization.

Attack Vector

The attack can be executed remotely over the network without requiring any prior authentication or user interaction. An attacker positioned on the network can potentially:

Capture authentication credentials or session tokens transmitted to/from the Azure Bastion service
Replay captured authentication data to bypass access controls
Escalate privileges within the Azure Bastion environment
Potentially access protected virtual machines and cloud resources that rely on Bastion for secure connectivity

The vulnerability mechanism involves intercepting and replaying authentication sequences. Technical details are available in the Microsoft Security Advisory.

Detection Methods for CVE-2025-49752

Indicators of Compromise

Unusual authentication patterns or repeated authentication attempts to Azure Bastion from unexpected source IPs
Anomalous privilege escalation events within Azure Bastion audit logs
Multiple authentication requests using identical or similar tokens within short time windows
Unexpected access to protected virtual machines through Bastion from unauthorized identities

Detection Strategies

Enable Azure Bastion diagnostic logging and forward logs to Azure Sentinel or your SIEM solution for analysis
Monitor Azure Activity Logs for unusual role assignments or privilege changes related to Bastion resources
Implement Azure Defender for cloud workload protection to detect anomalous authentication behaviors
Configure alerts for authentication anomalies including replay attack patterns in Azure AD Identity Protection

Monitoring Recommendations

Review Azure Bastion connection logs regularly for unauthorized access attempts
Implement continuous monitoring of Azure resource access patterns using Azure Monitor
Enable Microsoft Defender for Cloud to receive security recommendations and threat detection alerts
Audit all Bastion-accessible virtual machines for signs of unauthorized access

How to Mitigate CVE-2025-49752

Immediate Actions Required

Review and apply the latest security updates from Microsoft for Azure Bastion Developer
Audit Azure Bastion access logs for any signs of exploitation or unauthorized privilege escalation
Implement network segmentation to limit exposure of Azure Bastion deployments
Enable multi-factor authentication for all administrative accounts with access to Azure Bastion resources
Review and restrict role-based access control (RBAC) permissions for Azure Bastion

Patch Information

Microsoft has released a security update addressing this vulnerability. Organizations should consult the Microsoft Security Response Center advisory for official patch information and deployment guidance. As Azure Bastion is a managed service, ensure your deployment is configured to receive automatic updates or manually apply the latest service updates through the Azure portal.

Workarounds

Implement strict network access controls using Azure Network Security Groups to limit Bastion access to trusted IP ranges
Enable Azure Private Link for Azure Bastion to restrict access to private network traffic only
Implement Just-In-Time (JIT) VM access through Microsoft Defender for Cloud to reduce the attack surface
Consider temporary suspension of non-critical Bastion deployments until patches are applied
Enable conditional access policies in Azure AD requiring compliant devices and strong authentication

bash

# Azure CLI: Review Azure Bastion diagnostic settings
az monitor diagnostic-settings list --resource "/subscriptions/{subscription-id}/resourceGroups/{resource-group}/providers/Microsoft.Network/bastionHosts/{bastion-name}"

# Enable diagnostic logging for Azure Bastion
az monitor diagnostic-settings create \
  --name "BastionSecurityLogs" \
  --resource "/subscriptions/{subscription-id}/resourceGroups/{resource-group}/providers/Microsoft.Network/bastionHosts/{bastion-name}" \
  --logs '[{"category":"BastionAuditLogs","enabled":true}]' \
  --workspace "{log-analytics-workspace-id}"