CVE-2026-26118 Overview
CVE-2026-26118 is a Server-Side Request Forgery (SSRF) vulnerability affecting Azure MCP Server. This vulnerability allows an authorized attacker with low privileges to leverage the SSRF flaw to elevate privileges over a network. SSRF vulnerabilities enable attackers to induce the server-side application to make HTTP requests to an arbitrary domain of the attacker's choosing, potentially accessing internal services or cloud metadata endpoints that should not be externally accessible.
Critical Impact
An authenticated attacker can exploit this SSRF vulnerability to escalate privileges within the Azure environment, potentially gaining unauthorized access to internal resources, cloud metadata services, and sensitive configuration data.
Affected Products
- Azure MCP Server
Discovery Timeline
- 2026-03-10 - CVE-2026-26118 published to NVD
- 2026-03-11 - Last updated in NVD database
Technical Details for CVE-2026-26118
Vulnerability Analysis
This vulnerability is classified under CWE-918 (Server-Side Request Forgery), which occurs when a web application fetches a remote resource without properly validating the user-supplied URL. In the context of Azure MCP Server, an authenticated attacker can manipulate server-side requests to access internal resources that would otherwise be protected.
The SSRF vulnerability allows the attacker to bypass network security controls by leveraging the server's trust relationship with internal services. This is particularly dangerous in cloud environments like Azure, where metadata services at well-known IP addresses (such as 169.254.169.254) can expose sensitive information including access tokens, credentials, and instance configuration data.
Root Cause
The root cause of this vulnerability lies in insufficient validation of user-controlled input that is used to construct server-side HTTP requests. Azure MCP Server fails to properly sanitize or restrict URLs provided by authenticated users, allowing them to direct the server to make requests to arbitrary endpoints, including internal network resources and cloud metadata services.
Attack Vector
The attack is conducted over the network and requires low privileges (authentication). Once authenticated, the attacker can craft malicious requests that cause the Azure MCP Server to initiate connections to internal or restricted resources. This can be exploited to:
- Access cloud metadata endpoints to retrieve instance credentials
- Probe internal network services that are not directly accessible
- Bypass firewall and access control restrictions by pivoting through the trusted server
- Exfiltrate sensitive data from internal systems
The vulnerability does not require user interaction, making it exploitable in automated attack scenarios. Successful exploitation can result in high impact to confidentiality, integrity, and availability of the affected system.
Detection Methods for CVE-2026-26118
Indicators of Compromise
- Unusual outbound HTTP requests from Azure MCP Server to internal IP ranges (e.g., 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
- Requests to cloud metadata endpoints such as 169.254.169.254
- Unexpected access patterns from authenticated users targeting server-side URL parameters
- Anomalous network traffic originating from the MCP Server to previously uncontacted internal services
Detection Strategies
- Implement network-level monitoring to detect requests to cloud metadata services and internal IP ranges from the Azure MCP Server
- Deploy web application firewall (WAF) rules to detect and block SSRF patterns in user-supplied input
- Enable detailed logging for all HTTP requests made by the Azure MCP Server to identify suspicious destinations
- Use endpoint detection and response (EDR) solutions like SentinelOne to monitor for privilege escalation attempts following SSRF exploitation
Monitoring Recommendations
- Configure alerts for any Azure MCP Server connections to metadata endpoint 169.254.169.254
- Monitor authentication logs for accounts exhibiting unusual request patterns targeting URL manipulation
- Implement egress filtering and log all outbound connections from the Azure MCP Server
- Review Azure Activity Logs and Network Security Group flow logs for anomalous traffic patterns
How to Mitigate CVE-2026-26118
Immediate Actions Required
- Apply the latest security update from Microsoft as soon as available
- Implement network-level restrictions to prevent the Azure MCP Server from accessing internal IP ranges and cloud metadata endpoints
- Review and restrict permissions for authenticated users to minimize potential privilege escalation impact
- Enable enhanced logging and monitoring for the Azure MCP Server to detect exploitation attempts
Patch Information
Microsoft has released security guidance for this vulnerability. Administrators should refer to the Microsoft Security Update CVE-2026-26118 for official patch information and remediation steps. Apply the recommended security updates as soon as they become available in your Azure environment.
Workarounds
- Implement a strict allowlist for outbound connections from the Azure MCP Server, permitting only known required destinations
- Configure Instance Metadata Service (IMDS) to require session tokens, making SSRF attacks against metadata endpoints more difficult
- Deploy network segmentation to isolate the Azure MCP Server from sensitive internal resources
- Use a web application firewall (WAF) to filter requests containing internal IP addresses or metadata endpoint URLs in user-controlled parameters
# Example: Block outbound connections to metadata endpoint using Azure NSG
# Create outbound deny rule for metadata service
az network nsg rule create \
--resource-group <resource-group> \
--nsg-name <nsg-name> \
--name DenyMetadataOutbound \
--priority 100 \
--direction Outbound \
--access Deny \
--protocol Tcp \
--destination-address-prefixes 169.254.169.254 \
--destination-port-ranges 80 443
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
