CVE-2026-22739: Spring Cloud Path Traversal Vulnerability

CVE-2026-22739 Overview

A path traversal vulnerability exists in Spring Cloud Config Server when configured to use the native file system as a backend. The vulnerability allows an attacker to manipulate the profile parameter in requests to access files outside of the configured search directories, potentially exposing sensitive configuration files and system data.

Critical Impact

Attackers can exploit this path traversal vulnerability to read arbitrary files from the server's file system, potentially accessing sensitive configuration data, credentials, and other critical information stored outside the intended configuration directories.

Affected Products

• Spring Cloud versions 3.1.x before 3.1.13
• Spring Cloud versions 4.1.x before 4.1.9
• Spring Cloud versions 4.2.x before 4.2.3
• Spring Cloud versions 4.3.x before 4.3.2
• Spring Cloud versions 5.0.x before 5.0.2

Discovery Timeline

• 2026-03-24 - CVE CVE-2026-22739 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-22739

Vulnerability Analysis

This vulnerability is classified as CWE-22 (Path Traversal), which occurs when user-supplied input is not properly sanitized before being used in file system operations. In the context of Spring Cloud Config Server, the profile parameter accepts input that is used to construct file paths when retrieving configuration files from the native file system backend.

The Spring Cloud Config Server is designed to provide externalized configuration for distributed systems. When configured with the native file system as a backend, it serves configuration files from specified search directories. The vulnerability arises because the server fails to properly validate and sanitize the profile parameter, allowing attackers to inject path traversal sequences (such as ../) to escape the configured search directories and access arbitrary files on the server.

This vulnerability can be exploited remotely without authentication, potentially allowing attackers to read sensitive files including application configuration files, database credentials, API keys, and other secrets stored on the server's file system.

Root Cause

The root cause of this vulnerability lies in insufficient input validation of the profile parameter in the Spring Cloud Config Server's request handling logic. When processing requests for configuration files, the server uses the profile parameter to construct file paths without adequately sanitizing path traversal characters. This allows an attacker to craft malicious requests that include directory traversal sequences, enabling access to files outside the intended configuration directories.

Attack Vector

The attack is network-based and can be executed by sending specially crafted HTTP requests to the Spring Cloud Config Server endpoint. An attacker can manipulate the profile parameter to include path traversal sequences that navigate outside the configured search directories. No authentication or user interaction is required to exploit this vulnerability.

The typical attack flow involves:

1. Identifying a Spring Cloud Config Server instance configured with native file system backend
2. Crafting a request with a malicious profile parameter containing path traversal sequences
3. Sending the request to retrieve arbitrary files from the server's file system

For technical details on exploitation techniques, refer to the Spring Security Advisory CVE-2026-22739.

Detection Methods for CVE-2026-22739

Indicators of Compromise

• HTTP requests to Spring Cloud Config Server endpoints containing path traversal sequences (../, ..%2F, ..%5C) in the profile parameter
• Unusual access patterns to configuration endpoints with abnormally long or encoded parameter values
• Log entries showing requests attempting to access files outside configured search directories

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block path traversal patterns in request parameters
• Monitor Spring Cloud Config Server access logs for requests containing directory traversal sequences
• Deploy network intrusion detection systems (IDS) with signatures for path traversal attack patterns targeting Spring Cloud endpoints

Monitoring Recommendations

• Enable detailed logging for Spring Cloud Config Server to capture all incoming requests and parameters
• Set up alerts for HTTP 200 responses to requests containing suspicious path patterns, which may indicate successful exploitation
• Monitor file access patterns on the server hosting Spring Cloud Config Server for reads of sensitive files outside configuration directories

How to Mitigate CVE-2026-22739

Immediate Actions Required

• Upgrade Spring Cloud to the patched versions: 3.1.13, 4.1.9, 4.2.3, 4.3.2, or 5.0.2 depending on your version branch
• Review server logs for any suspicious requests that may indicate previous exploitation attempts
• Audit files accessible to the Spring Cloud Config Server process to assess potential exposure

Patch Information

VMware has released security updates to address this vulnerability. Organizations should upgrade to the following fixed versions based on their current Spring Cloud deployment:

For complete patch details and upgrade instructions, refer to the Spring Security Advisory CVE-2026-22739.

Workarounds

• Restrict network access to Spring Cloud Config Server endpoints to trusted internal networks only using firewall rules or network segmentation
• Implement a reverse proxy or WAF in front of the Config Server to filter and block requests containing path traversal patterns
• Consider switching to an alternative configuration backend (Git, Vault) that is not affected by this file system-specific vulnerability

# Example: Restrict Config Server access using iptables
# Allow only internal network (10.0.0.0/8) to access Config Server port
iptables -A INPUT -p tcp --dport 8888 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8888 -j DROP