CVE-2026-26120: Microsoft Bing SSRF Vulnerability

CVE-2026-26120 Overview

CVE-2026-26120 is a Server-Side Request Forgery (SSRF) vulnerability affecting Microsoft Bing that allows an unauthorized attacker to perform tampering over a network. This vulnerability enables attackers to induce the server-side application to make HTTP requests to an arbitrary domain of the attacker's choosing, potentially leading to unauthorized access to internal resources, data exfiltration, or further exploitation of backend systems.

Critical Impact

Unauthorized attackers can exploit this SSRF vulnerability to access internal network resources, bypass access controls, and perform unauthorized actions through Microsoft Bing's server infrastructure.

Affected Products

• Microsoft Bing

Discovery Timeline

• March 19, 2026 - CVE-2026-26120 published to NVD
• March 19, 2026 - Last updated in NVD database

Technical Details for CVE-2026-26120

Vulnerability Analysis

This SSRF vulnerability (CWE-918) in Microsoft Bing allows unauthorized network-based attackers to manipulate server-side requests without requiring any user interaction or authentication. The vulnerability enables attackers to forge requests from the vulnerable server, potentially accessing internal services that would otherwise be inaccessible from external networks.

The attack can be executed remotely over the network and does not require elevated privileges or user interaction, making it accessible to a wide range of potential attackers. The vulnerability primarily impacts confidentiality through potential information disclosure and availability through service disruption capabilities.

Root Cause

The root cause of CVE-2026-26120 lies in improper input validation of user-supplied URLs or request parameters that are subsequently used in server-side HTTP requests. The application fails to adequately restrict or sanitize destination URLs, allowing attackers to redirect requests to arbitrary internal or external endpoints. This weakness is classified under CWE-918 (Server-Side Request Forgery).

Attack Vector

The attack is network-based and can be executed by unauthorized attackers without authentication. An attacker can craft malicious requests containing specially formatted URLs or parameters that cause the Microsoft Bing server to make requests to unintended destinations. This can include:

• Internal network resources and services
• Cloud metadata endpoints (such as 169.254.169.254)
• Internal APIs and administrative interfaces
• Other backend systems accessible from the server

The vulnerability allows attackers to bypass network segmentation and access controls by leveraging the trusted server's network position to reach otherwise protected resources.

Detection Methods for CVE-2026-26120

Indicators of Compromise

• Unusual outbound HTTP/HTTPS requests from Bing servers to internal IP ranges (e.g., 10.x.x.x, 172.16.x.x, 192.168.x.x)
• Requests to cloud metadata endpoints (e.g., 169.254.169.254) from application servers
• Anomalous DNS lookups for internal hostnames originating from web-facing services
• Unexpected connections to non-standard ports from the application tier

Detection Strategies

• Implement network monitoring to detect server-side requests to internal IP addresses or localhost
• Deploy web application firewalls (WAF) with SSRF detection rules
• Monitor for unusual URL patterns in application logs containing internal IP addresses or reserved hostnames
• Enable logging of all outbound requests from web application servers

Monitoring Recommendations

• Configure alerts for outbound connections from web servers to private IP ranges
• Monitor DNS query logs for suspicious internal hostname resolutions from public-facing services
• Implement egress filtering and monitor for policy violations
• Review application logs for URL parameters containing IP addresses or internal hostnames

How to Mitigate CVE-2026-26120

Immediate Actions Required

• Review and apply any available patches or mitigations from Microsoft
• Implement network-level controls to restrict outbound connections from affected systems
• Deploy WAF rules to block SSRF attack patterns
• Audit application logs for evidence of exploitation attempts

Patch Information

Microsoft has published a security advisory for this vulnerability. Organizations should refer to the Microsoft CVE-2026-26120 Advisory for official patch information and remediation guidance. As this is a cloud-based service, Microsoft manages the patching process, but organizations should verify their configurations align with security best practices.

Workarounds

• Implement strict allowlisting for any user-supplied URLs that are used in server-side requests
• Block outbound requests to private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 127.0.0.0/8)
• Disable unnecessary HTTP redirects in server-side request handling
• Deploy network segmentation to limit the impact of potential SSRF exploitation
• Monitor and restrict access to cloud metadata endpoints from application servers