CVE-2020-5410: Spring Cloud Config Path Traversal Flaw

CVE-2020-5410 Overview

Spring Cloud Config, a critical component in distributed configuration management for cloud-native applications, is affected by a directory traversal vulnerability that allows attackers to access arbitrary configuration files through the spring-cloud-config-server module. A malicious user can send a request using a specially crafted URL that can lead to a directory traversal attack, potentially exposing sensitive configuration data including database credentials, API keys, and other secrets stored on the server.

Critical Impact

This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild. Attackers can read arbitrary files from the configuration server, potentially compromising sensitive credentials and application secrets.

Affected Products

• VMware Spring Cloud Config versions 2.2.x prior to 2.2.3
• VMware Spring Cloud Config versions 2.1.x prior to 2.1.9
• Older unsupported versions of VMware Spring Cloud Config

Discovery Timeline

• 2020-06-02 - CVE-2020-5410 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2020-5410

Vulnerability Analysis

This directory traversal vulnerability (CWE-22, CWE-23) exists in the spring-cloud-config-server module, which is responsible for serving configuration files to client applications in a Spring Cloud environment. The vulnerability stems from insufficient validation of user-supplied input in URL path parameters, allowing attackers to break out of the intended directory structure and access files outside the configuration repository.

The spring-cloud-config-server acts as a centralized configuration service that typically stores sensitive application properties including database connection strings, encryption keys, OAuth credentials, and service account tokens. When exploited, this vulnerability grants unauthenticated remote attackers read access to arbitrary files accessible by the server process, creating significant data exposure risks.

Root Cause

The root cause of this vulnerability is improper input validation in the URL path handling logic within the spring-cloud-config-server module. The server fails to properly sanitize path traversal sequences (such as ../ or encoded variants) in incoming requests, allowing attackers to navigate outside the designated configuration directories. This represents a classic path traversal weakness where user-controlled input is used to construct file paths without adequate validation or canonicalization.

Attack Vector

The attack is conducted remotely over the network without requiring authentication or user interaction. An attacker can craft malicious HTTP requests containing directory traversal sequences to access files outside the intended configuration directory. The attack targets the configuration server endpoint and can be executed by any network-accessible client.

By manipulating the URL path with traversal sequences like ../ or URL-encoded equivalents such as %2e%2e%2f, an attacker can traverse parent directories and read sensitive files from the server's filesystem. This could include accessing /etc/passwd, application configuration files, private keys, or any other files readable by the Spring Cloud Config server process. See the VMware Security Advisory for detailed technical information on exploitation patterns.

Detection Methods for CVE-2020-5410

Indicators of Compromise

• HTTP requests to Spring Cloud Config server endpoints containing ../ or URL-encoded path traversal sequences (%2e%2e%2f, %252e%252e%252f)
• Unusual access patterns to configuration endpoints with long or malformed URL paths
• Server logs showing requests for files outside the configuration repository root
• Unexpected file read operations from the spring-cloud-config-server process

Detection Strategies

• Monitor HTTP access logs for path traversal patterns in requests to /config/ or configuration server endpoints
• Implement web application firewall (WAF) rules to block requests containing directory traversal sequences
• Deploy network intrusion detection signatures for CVE-2020-5410 exploitation attempts
• Review application logs for configuration file access outside expected directories

Monitoring Recommendations

• Enable verbose logging on Spring Cloud Config server instances to capture all configuration requests
• Configure SIEM alerts for path traversal patterns in web server access logs
• Monitor file system access patterns from Java/Spring processes for anomalous file reads
• Track network connections to configuration server ports (typically 8888) for suspicious activity

How to Mitigate CVE-2020-5410

Immediate Actions Required

• Upgrade Spring Cloud Config to version 2.2.3 or later for the 2.2.x branch
• Upgrade Spring Cloud Config to version 2.1.9 or later for the 2.1.x branch
• If immediate patching is not possible, restrict network access to the Spring Cloud Config server to trusted clients only
• Review server logs for evidence of exploitation attempts

Patch Information

VMware has released patches addressing this vulnerability. Organizations should upgrade to Spring Cloud Config version 2.2.3 or later for the 2.2.x release train, or version 2.1.9 or later for the 2.1.x release train. Detailed patch information is available in the VMware Security Advisory. Given this vulnerability's inclusion in the CISA Known Exploited Vulnerabilities Catalog, patching should be treated as a high priority.

Workarounds

• Place the Spring Cloud Config server behind a reverse proxy or WAF that filters path traversal attempts
• Restrict network access to the configuration server using firewall rules, allowing only trusted application servers
• Implement authentication and authorization on the configuration server if not already in place
• Run the Spring Cloud Config server with minimal filesystem permissions to limit the impact of potential exploitation

# Example: Restrict access to Spring Cloud Config server using iptables
# Allow only specific application servers to access config server on port 8888
iptables -A INPUT -p tcp --dport 8888 -s 10.0.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8888 -j DROP