CVE-2026-47879 in Spring Cloud Gateway
Summary
by MITRE • 08/27/2026
Spring Cloud Gateway JsonToGrpcGatewayFilterFactory allows arbitrary Spring Resource locations for defining the proto descriptor. Spring Cloud Gateway 5.0.0 - 5.0.2 Spring Cloud Gateway 4.3.0 - 4.3.5 Spring Cloud Gateway 4.0.0 - 4.2.9 Spring Cloud Gateway 3.1.13 and earlier
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Analysis
by VulDB Data Team • 08/27/2026
The vulnerability identified in Spring Cloud Gateway affects the JsonToGrpcGatewayFilterFactory component, which is responsible for transforming JSON payloads into gRPC requests within microservice architectures. This specific flaw arises from an insecure deserialization or path traversal mechanism inherent in how the filter processes configuration parameters related to proto descriptors. Specifically, the factory allows developers and administrators to specify arbitrary Spring Resource locations when defining these descriptor files. In a typical deployment, this feature is intended for loading protocol buffer definitions from trusted classpath resources or local file systems during application startup. However, due to insufficient validation of user-supplied input used to configure this filter, an attacker can manipulate the resource location parameter to point to sensitive system files rather than legitimate proto descriptors.
This technical flaw effectively constitutes a Local File Inclusion (LFI) vulnerability, categorized under CWE-22: Improper Limitation of a Pathname to a Restricted Directory in the Common Weakness Enumeration standards. By exploiting this weakness, an attacker can read arbitrary files from the underlying operating system where the Spring Cloud Gateway instance is running. The impact extends beyond simple data exfiltration; depending on the context and permissions of the service account executing the gateway, this could lead to the disclosure of sensitive configuration files, environment variables containing credentials, private keys, or internal network topology details stored in local configurations. In severe cases where file contents can be further processed by other components of the application stack, it may facilitate more complex attacks such as remote code execution through crafted input that triggers subsequent parsing errors or logic flaws.
From an operational perspective, this vulnerability poses a significant risk to organizations utilizing Spring Cloud Gateway for API management and service mesh routing. Since gateways often sit at the edge of internal networks, exposing them to file read vulnerabilities compromises the integrity of the entire microservice ecosystem. Attackers can leverage these disclosed files to perform lateral movement within the network or escalate privileges by obtaining administrative credentials stored in configuration properties like application.yml or bootstrap.properties. The vulnerability is present across multiple versions including Spring Cloud Gateway 5.0.0 through 5.0.2, 4.3.0 through 4.3.5, 4.0.0 through 4.2.9, and version 3.1.13 and earlier, indicating a long-standing issue in the design of how resource locations are handled within this specific filter factory.
Mitigation strategies should prioritize immediate patching to the latest stable release where this flaw has been addressed by the Spring Framework team. For environments that cannot be immediately updated due to compatibility constraints or operational dependencies, defensive coding practices must be implemented. Developers should avoid passing user-controlled input directly into parameters that determine resource locations without rigorous validation. Input sanitization techniques such as strict allow-listing of expected file paths and ensuring that only resources from the classpath are accessible can help mitigate this risk. Additionally, deploying Web Application Firewalls with rules capable of detecting path traversal patterns in HTTP headers or query parameters may provide a layer of defense against exploitation attempts while permanent fixes are applied.
The ATT&CK framework maps this vulnerability to techniques involving Initial Access and Collection phases, specifically T1083: File and Directory Discovery if the attacker uses it for reconnaissance, or T1560: Archive Collected Data if sensitive files are extracted. Security teams should monitor access logs for unusual requests targeting configuration endpoints that utilize the JsonToGrpcGatewayFilterFactory. Implementing least-privilege principles for the service account running the gateway application is also critical to limit the scope of damage in case an exploitation attempt succeeds. Regular vulnerability scanning and code reviews focusing on how external inputs interact with file system operations are essential preventive measures against such insecure deserialization and path traversal flaws.