Overview
CVE-2026-47879 is a vulnerability in the Spring Cloud Gateway's `JsonToGrpcGatewayFilterFactory` that allows arbitrary Spring Resource locations for defining the proto descriptor. This vulnerability affects Spring Cloud Gateway versions 5.0.0 - 5.0.2, 4.3.0 - 4.3.5, 4.0.0 - 4.2.9, and 3.1.13 and earlier. With a CVSS score of 7.7, this vulnerability is considered high-severity and could allow attackers to access sensitive data or disrupt service operations.
Understanding the Vulnerability / Threat
Root Cause Analysis
The root cause of this vulnerability is the lack of proper validation and sanitization of user-input data in the `JsonToGrpcGatewayFilterFactory` component of Spring Cloud Gateway. Specifically, the vulnerability allows arbitrary Spring Resource locations for defining the proto descriptor, which can lead to unauthorized access to sensitive data or disruption of service operations.
This vulnerability belongs to the CWE-918 category, which involves server-side request forgery (SSRF) attacks.
Attack Surface & Vector
The attack surface for this vulnerability is the network, as it can be exploited remotely without requiring any user interaction. The attack vector involves sending a crafted request to the Spring Cloud Gateway instance, which can trigger the vulnerability.
The preconditions for exploiting this vulnerability include having network access to the Spring Cloud Gateway instance and being able to send crafted requests to it.
Exploitation Mechanics — Scenario Walkthrough
Scenario: Compromising a Corporate Spring Cloud Gateway Instance
1. Initial Position: An attacker gains network access to a corporate Spring Cloud Gateway instance.
2. Triggering the Flaw: The attacker crafts a request to the Spring Cloud Gateway instance with a malicious proto descriptor that defines an arbitrary Spring Resource location.
3. What Breaks: The `JsonToGrpcGatewayFilterFactory` component processes the request and allows the arbitrary Spring Resource location, potentially leading to unauthorized access to sensitive data or disruption of service operations.
4. Attacker's Prize: The attacker gains access to sensitive data or disrupts service operations, potentially leading to lateral movement, data exfiltration, or other malicious activities.
Real-World Impact
The real-world impact of this vulnerability can be significant, as it can allow attackers to access sensitive data or disrupt service operations. If actively exploited in the wild, this vulnerability could lead to:
* Data theft or exfiltration
* Lateral movement within the network
* Disruption of service operations
* Potential for ransomware deployment or other malicious activities
Detection & Defense
Immediate Mitigations
To mitigate this vulnerability, users should upgrade to the following versions:
* Spring Cloud Gateway 5.0.3 or later
* Spring Cloud Gateway 4.3.6 or later
* Spring Cloud Gateway 4.2.10 or later
* Spring Cloud Gateway 3.1.14 or later
Detection Strategies
Defenders can detect exploitation attempts by monitoring for suspicious requests to the Spring Cloud Gateway instance, such as requests with malformed or suspicious proto descriptors. SIEM rules and network signatures can be used to detect and alert on potential exploitation attempts.
Long-Term Hardening
To prevent this class of vulnerability, users should implement defense-in-depth strategies, such as:
* Validating and sanitizing user-input data
* Implementing strict access controls and authentication mechanisms
* Regularly updating and patching software dependencies
* Monitoring for suspicious activity and implementing incident response plans
Key Takeaways
* CVE-2026-47879 is a high-severity vulnerability in Spring Cloud Gateway that allows arbitrary Spring Resource locations for defining the proto descriptor.
* The vulnerability can be exploited remotely without requiring user interaction.
* Users should upgrade to patched versions and implement defense-in-depth strategies to prevent this class of vulnerability.
* Defenders should monitor for suspicious requests and implement detection and incident response plans.
Sources
* National Vulnerability Database (NVD)
* Spring Security CVE page