CVE-2025-41242: Spring Framework Path Traversal Flaw

CVE-2025-41242 Overview

CVE-2025-41242 is a Path Traversal vulnerability affecting Spring Framework MVC applications when deployed on non-compliant Servlet containers. This vulnerability allows attackers to potentially access files outside the intended directory structure through specially crafted requests targeting static resource handling.

An application is vulnerable when all of the following conditions are true:

• The application is deployed as a WAR file or with an embedded Servlet container
• The Servlet container does not reject suspicious URI sequences as defined in the Jakarta Servlet 6.1 specification
• The application serves static resources using Spring's resource handling functionality

Critical Impact

Attackers can exploit this path traversal vulnerability to read sensitive files from the server, potentially exposing configuration files, credentials, or other confidential data. Applications on non-compliant Servlet containers serving static resources are at risk.

Affected Products

• Spring Framework MVC applications deployed as WAR files
• Spring Framework MVC applications with embedded Servlet containers
• Applications using Spring resource handling for static resources on non-compliant Servlet containers

Discovery Timeline

• 2025-08-18 - CVE CVE-2025-41242 published to NVD
• 2025-08-25 - Last updated in NVD database

Technical Details for CVE-2025-41242

Vulnerability Analysis

This vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory) occurs when Spring Framework MVC applications handle static resource requests without proper path canonicalization. The Jakarta Servlet specification defines security requirements for URI path canonicalization, specifically that Servlet containers should reject suspicious sequences. However, when deployed on a Servlet container that does not enforce these security measures, Spring's static resource handling can be exploited to traverse outside the intended resource directory.

The attack requires network access but involves high complexity, as it depends on specific deployment configurations where the Servlet container's default security features are either missing or disabled. While Apache Tomcat and Eclipse Jetty are verified to be safe when using their default security configurations, other Servlet containers or custom configurations may be vulnerable.

Root Cause

The root cause lies in the interaction between Spring Framework's static resource handling and Servlet containers that fail to properly canonicalize and validate URI paths. When a Servlet container does not reject path traversal sequences (such as ../ or encoded variants), these malicious sequences can be passed through to Spring's resource resolution logic. Without proper validation at the Servlet container level, attackers can craft requests that escape the intended static resource directory.

Attack Vector

The attack is conducted remotely over the network. An attacker sends HTTP requests to the application's static resource endpoints with path traversal sequences embedded in the URL. The malicious request attempts to navigate outside the designated static resources directory to access arbitrary files on the server filesystem.

The attack flow involves:

1. Identifying an application endpoint that serves static resources through Spring's resource handling
2. Crafting a request with path traversal sequences (potentially URL-encoded to bypass basic filters)
3. Exploiting the Servlet container's failure to canonicalize the path
4. Accessing sensitive files outside the intended resource directory, resulting in information disclosure

For detailed technical information, refer to the Spring Security Advisory for CVE-2025-41242.

Detection Methods for CVE-2025-41242

Indicators of Compromise

• HTTP requests to static resource endpoints containing path traversal sequences such as ../, ..%2f, %2e%2e/, or similar encoded variants
• Unusual access patterns to static resource URLs with abnormally long or suspicious path segments
• Log entries showing attempts to access files outside the configured static resource directories
• Increased 404 or 500 errors on static resource endpoints indicating traversal probing

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block path traversal patterns in incoming requests
• Enable detailed access logging on the Servlet container and monitor for suspicious URI patterns
• Use SentinelOne's Singularity Platform to detect anomalous file access patterns from the Java process serving the application
• Review application logs for requests containing encoded directory traversal characters

Monitoring Recommendations

• Monitor HTTP request logs for path traversal indicators in static resource requests
• Set up alerts for file access attempts outside designated web directories from the application server process
• Implement real-time monitoring of static resource request patterns for anomalies
• Track and alert on changes to sensitive configuration files that could indicate successful exploitation

How to Mitigate CVE-2025-41242

Immediate Actions Required

• Upgrade Spring Framework to the latest patched version as recommended in the security advisory
• Verify that your Servlet container (Apache Tomcat, Eclipse Jetty, etc.) is configured with default security features enabled
• Review and audit static resource handling configurations in your Spring MVC applications
• If running on a non-standard Servlet container, verify its compliance with Jakarta Servlet 6.1 URI canonicalization requirements

Patch Information

Spring has released security patches addressing this vulnerability. Consult the official Spring Security Advisory for the specific versions containing the fix and detailed upgrade instructions. The advisory provides version-specific guidance for Spring Framework applications.

Workarounds

• Ensure your Servlet container (Tomcat, Jetty) has default security configurations enabled that reject suspicious path sequences
• Implement a servlet filter or reverse proxy rule to validate and reject requests containing path traversal patterns before they reach Spring's resource handling
• Restrict static resource serving to a dedicated, isolated directory with minimal permissions
• Consider disabling Spring's static resource handling and serving static content through a dedicated web server or CDN

If immediate patching is not possible, implement request filtering at the application or infrastructure level:

# Example: Apache mod_security rule to block path traversal attempts
# Add to your Apache configuration or mod_security rules

SecRule REQUEST_URI "@contains ../" \
    "id:100001,phase:1,deny,status:403,msg:'Path traversal attempt blocked'"
SecRule REQUEST_URI "@contains ..%2f" \
    "id:100002,phase:1,deny,status:403,msg:'Encoded path traversal blocked'"
SecRule REQUEST_URI "@contains %2e%2e" \
    "id:100003,phase:1,deny,status:403,msg:'Double-encoded traversal blocked'"