CVE-2025-64657: Azure Application Gateway Privilege Escalation

CVE-2025-64657 Overview

A stack-based buffer overflow vulnerability exists in Microsoft Azure Application Gateway that allows an unauthorized attacker to elevate privileges over a network. This vulnerability, classified as CWE-787 (Out-of-bounds Write), can be exploited remotely without requiring authentication or user interaction, making it a significant threat to organizations utilizing Azure Application Gateway for their web application delivery and security needs.

Critical Impact

An unauthenticated remote attacker can exploit this stack-based buffer overflow to achieve privilege escalation, potentially gaining full control over affected Azure Application Gateway instances and compromising the security of backend applications.

Affected Products

• Microsoft Azure Application Gateway

Discovery Timeline

• 2025-11-26 - CVE-2025-64657 published to NVD
• 2026-02-13 - Last updated in NVD database

Technical Details for CVE-2025-64657

Vulnerability Analysis

This vulnerability represents a stack-based buffer overflow condition in Azure Application Gateway, a web traffic load balancer that enables organizations to manage traffic to their web applications. The flaw stems from improper handling of input data, which allows an attacker to write data beyond the boundaries of allocated stack memory. When exploited, this out-of-bounds write condition can corrupt adjacent memory structures, potentially allowing the attacker to hijack execution flow and escalate privileges within the affected system.

The attack can be executed remotely over the network without requiring any prior authentication or user interaction, significantly lowering the barrier for exploitation. Successful exploitation could result in complete compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause of CVE-2025-64657 is an out-of-bounds write vulnerability (CWE-787) in the Azure Application Gateway component. This occurs when the application fails to properly validate the size or boundaries of input data before copying it to a fixed-size buffer on the stack. When oversized or malformed input is processed, the data overflows the intended buffer boundaries, overwriting adjacent stack memory including return addresses, saved registers, or other critical data structures.

Attack Vector

The attack vector for this vulnerability is network-based, allowing remote exploitation. An attacker can send specially crafted network requests to a vulnerable Azure Application Gateway instance. The malicious payload would be designed to trigger the buffer overflow condition, overwriting stack memory with attacker-controlled data. By carefully crafting the payload, an attacker can manipulate the execution flow to elevate privileges, potentially gaining unauthorized administrative access to the gateway and its managed resources.

The attack requires no authentication credentials and no interaction from legitimate users, making it particularly dangerous in environments where Azure Application Gateway is exposed to untrusted networks.

Detection Methods for CVE-2025-64657

Indicators of Compromise

• Unexpected crashes or restarts of Azure Application Gateway services
• Anomalous network traffic patterns including oversized or malformed HTTP requests targeting the gateway
• Unusual privilege escalation events or unauthorized administrative actions in Azure audit logs
• Memory corruption artifacts or stack corruption indicators in diagnostic logs

Detection Strategies

• Monitor Azure Application Gateway access logs for abnormally large request headers or payloads that could indicate buffer overflow attempts
• Enable Azure Security Center threat detection to identify exploitation attempts against Azure resources
• Implement network intrusion detection rules to flag suspicious traffic patterns targeting Application Gateway endpoints
• Review Azure Activity Logs for unexpected configuration changes or privilege escalation events

Monitoring Recommendations

• Enable comprehensive logging for Azure Application Gateway including access logs, firewall logs, and diagnostic logs
• Configure Azure Monitor alerts for anomalous request patterns and gateway health degradation
• Implement continuous monitoring of Azure AD audit logs for unauthorized privilege escalation attempts
• Utilize Azure Sentinel or equivalent SIEM for correlation and analysis of security events across the Azure environment

How to Mitigate CVE-2025-64657

Immediate Actions Required

• Review the Microsoft Security Advisory for the latest guidance and patches
• Audit Azure Application Gateway configurations and restrict network access to trusted sources where possible
• Enable Azure Web Application Firewall (WAF) with the latest rule sets to help mitigate potential exploitation attempts
• Monitor Azure Application Gateway instances for signs of compromise or unusual activity

Patch Information

Microsoft has published security guidance for this vulnerability. Organizations should consult the Microsoft Security Advisory for detailed patch information and remediation steps. As Azure Application Gateway is a managed cloud service, Microsoft may apply security updates automatically, but organizations should verify their instances are protected and follow any additional guidance provided.

Workarounds

• Implement network segmentation to limit exposure of Azure Application Gateway to untrusted networks
• Enable Azure Web Application Firewall (WAF) with custom rules to inspect and block potentially malicious oversized requests
• Configure Azure Network Security Groups to restrict inbound traffic to Application Gateway from known, trusted IP ranges only
• Consider implementing Azure DDoS Protection to help mitigate network-based attack vectors

As Azure Application Gateway is a managed service, configuration-level mitigations should be applied through the Azure portal, CLI, or ARM templates according to Microsoft's recommended security baseline practices.