Attackers Bypass Authentication and Escalate Privileges via Critical Azure Bastion Vulnerability

Microsoft Azure Bastion, the cloud giant’s managed service for secure remote access to virtual machines, faces a critical authentication bypass vulnerability that could allow attackers to gain administrative control over entire cloud infrastructures with minimal effort.

CVE-2025-49752, disclosed on November 20, 2025, poses a significant security risk to enterprises that rely on Azure Bastion for centralized RDP and SSH connectivity management.

Authentication Bypass Enables Instant Privilege Escalation

The vulnerability exploits a fundamental flaw in Azure Bastion’s authentication mechanisms, classified as CWE-294 (Authentication Bypass by Capture-replay).

Attackers can intercept and replay valid authentication tokens to gain unauthorized administrative access to all virtual machines connected through the affected Bastion host.

The attack requires only a single network request and operates without user interaction, making it trivially exploitable for even moderately skilled threat actors.

With a maximum CVSS score of 10.0, CVE-2025-49752 ranks among the most dangerous cloud vulnerabilities discovered this year.

Remote exploitation requires no prior authentication or special privileges, meaning any internet-connected attacker can potentially compromise connected infrastructure.

Organizations running Azure Bastion deployments are urged to apply security updates immediately.

Microsoft has not published specific version numbers affected by this vulnerability, meaning all Azure Bastion deployments before the November 20, 2025, security patch are potentially vulnerable.

Any configuration that uses Azure Bastion for RDP or SSH access creates an attack surface for privilege escalation attempts.

This marks the third critical privilege escalation vulnerability in Microsoft Azure services discovered in 2025, following CVE-2025-54914 (Azure Networking, CVSS 10.0) and CVE-2025-29827 (Azure Automation, CVSS 9.9).

The pattern suggests systematic weaknesses in Azure’s authentication framework despite Microsoft’s Secure Future Initiative aimed at improving security development practices.

Organizations should prioritize applying the November 20, 2025, security patch to all Azure Bastion deployments.

Until patching is complete, administrators should implement network segmentation to limit exposure and monitor Bastion access logs for suspicious authentication attempts or unusual token replay activity.

CVE ID	CVSS	Attack Vector	Complexity	Authentication Required
CVE-2025-49752	10.0	Network	Low	None
CWE Classification	CWE-294	Affected Component	Azure Bastion	Publication Date

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