CVE-2025-41235: Spring Cloud Gateway SSRF Vulnerability

CVE-2025-41235 Overview

CVE-2025-41235 is a high-severity HTTP Request Smuggling vulnerability (CWE-444) affecting Spring Cloud Gateway Server. The vulnerability occurs when the server improperly forwards X-Forwarded-For and Forwarded headers from untrusted proxies without proper validation. This behavior allows attackers to manipulate header values and potentially bypass security controls, spoof client IP addresses, or circumvent access restrictions that rely on IP-based authentication.

Critical Impact

Attackers can exploit this vulnerability to bypass IP-based access controls, spoof client identities, and potentially circumvent security mechanisms that rely on trusted proxy header validation in Spring Cloud Gateway deployments.

Affected Products

• Spring Cloud Gateway Server (versions prior to patch)

Discovery Timeline

• 2025-05-30 - CVE CVE-2025-41235 published to NVD
• 2025-05-30 - Last updated in NVD database

Technical Details for CVE-2025-41235

Vulnerability Analysis

This vulnerability represents an HTTP Request Smuggling issue classified under CWE-444 (Inconsistent Interpretation of HTTP Requests). Spring Cloud Gateway Server fails to properly validate the source of X-Forwarded-For and Forwarded headers before forwarding them to backend services. In properly configured environments, these headers should only be trusted when originating from known, trusted proxy servers.

When an attacker sends requests directly to the Spring Cloud Gateway Server with spoofed X-Forwarded-For or Forwarded headers, the gateway blindly forwards these headers to downstream services. This creates a significant security gap for applications that rely on these headers for client identification, IP-based access control, rate limiting, or audit logging.

The network-accessible nature of this vulnerability allows remote unauthenticated attackers to exploit it without any user interaction, resulting in high impact to system integrity while confidentiality and availability remain unaffected.

Root Cause

The root cause lies in Spring Cloud Gateway Server's insufficient validation of the trustworthiness of incoming proxy headers. The server does not properly distinguish between headers received from trusted internal proxies versus headers that may have been injected by external, untrusted sources. This allows the header chain to be manipulated before reaching backend services.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can craft HTTP requests containing forged X-Forwarded-For or Forwarded headers and send them directly to the Spring Cloud Gateway endpoint. When the gateway forwards these requests to backend services, the spoofed headers are preserved, leading backend applications to trust falsified client information.

This can enable various attack scenarios including IP spoofing to bypass geographic restrictions or IP whitelists, circumventing rate limiting mechanisms, manipulating audit logs to hide attacker origin, and bypassing IP-based authentication or authorization controls.

Detection Methods for CVE-2025-41235

Indicators of Compromise

• Unusual patterns in X-Forwarded-For header chains with unexpected or internal IP addresses appearing in external requests
• Requests containing Forwarded headers with inconsistent client IP information compared to the actual connection source
• Backend application logs showing client IPs that don't match expected geographic or network patterns
• Anomalous access patterns from normally restricted IP ranges

Detection Strategies

• Implement header validation at the gateway level to detect requests with suspicious X-Forwarded-For patterns
• Deploy network monitoring to identify direct external connections to gateway endpoints with proxy headers
• Configure backend services to log and alert on IP address mismatches between connection source and forwarded headers
• Use SentinelOne's application detection capabilities to monitor Spring Cloud Gateway behavior for header manipulation attempts

Monitoring Recommendations

• Enable detailed access logging on Spring Cloud Gateway instances with full header capture
• Monitor for requests where the actual source IP differs significantly from the X-Forwarded-For value
• Set up alerts for high volumes of requests claiming to originate from internal network ranges
• Implement correlation rules to detect IP spoofing attempts across gateway and backend service logs

How to Mitigate CVE-2025-41235

Immediate Actions Required

• Review and update Spring Cloud Gateway Server to the latest patched version
• Configure explicit trusted proxy lists to ensure only headers from known proxies are accepted
• Implement input validation for X-Forwarded-For and Forwarded headers at the gateway level
• Audit backend services that rely on forwarded headers for access control decisions

Patch Information

VMware/Spring has released a security advisory for this vulnerability. Refer to the Spring Security CVE-2025-41235 advisory for official patch information and updated versions. Organizations should upgrade to the patched version as soon as possible to remediate this vulnerability.

Workarounds

• Configure Spring Cloud Gateway to explicitly define trusted proxy addresses and reject forwarded headers from untrusted sources
• Implement a reverse proxy or web application firewall (WAF) in front of the gateway to strip or validate incoming proxy headers
• Use network segmentation to ensure the gateway only receives traffic from known, trusted sources
• Apply IP-based access controls at the network level rather than relying solely on application-level header validation

For proper gateway configuration, consult the Spring Security CVE-2025-41235 advisory for vendor-recommended configuration changes and workarounds specific to your deployment architecture.