Apache Struts Disk Exhaustion Vulnerability (CVE-2025-64775): Risks, Impacts, and Mitigation Strategies

Recently discovered Apache Struts flaw tracked as CVE-2025-64775 poses a serious threat to web applications worldwide. This vulnerability allows attackers to launch disk exhaustion attacks, overwhelming servers by filling storage space and causing denial-of-service (DoS) disruptions. As a widely used open-source Java framework for building web apps, Apache Struts powers thousands of enterprise systems, making this issue critical for immediate attention.

In 2025, security researchers identified how malicious requests exploit Struts’ file handling mechanisms, leading to uncontrolled disk usage. Affected versions range from Struts 2.0 to 6.3.x, with no authentication required for exploitation. This article breaks down the vulnerability, its mechanics, real-world implications, and step-by-step fixes to help developers and IT teams safeguard their environments.

What Is the Apache Struts Disk Exhaustion Vulnerability CVE-2025-64775?

The Apache Struts flaw CVE-2025-64775 stems from improper handling of temporary files during request processing in the Struts framework. Attackers can send specially crafted HTTP requests that trigger the creation of massive temporary files on the server disk, rapidly consuming available storage until the system crashes.

This is classified as a high-severity DoS vulnerability with a CVSS score of 7.5 out of 10, according to the National Vulnerability Database (NVD). It affects the core dispatching functionality, where user-supplied data influences file I/O operations without adequate size limits or cleanup routines.

“Disk exhaustion attacks like CVE-2025-64775 exploit resource management flaws, turning everyday web traffic into a weapon against availability.” – Security analyst report, 2025

How Does This Differ from Previous Struts Vulnerabilities?

Unlike remote code execution flaws such as CVE-2017-5638 that led to the Equifax breach, this Apache Struts disk exhaustion vulnerability focuses on resource denial rather than code injection. Past issues targeted OGNL expressions, while CVE-2025-64775 abuses multipart file uploads and session temp dirs.

• Exploitation requires no privileges – fully remote and unauthenticated.
• No payloads needed beyond oversized or looped requests.
• Impacts Java-based apps on Tomcat, JBoss, and other servlet containers.

How Do Disk Exhaustion Attacks Work in Apache Struts?

Disk exhaustion attacks in Apache Struts exploit gaps in the framework’s Action and Interceptor components. Here’s a step-by-step breakdown of how attackers weaponize CVE-2025-64775:

1. Craft Malicious Request: Attacker sends a POST request with manipulated multipart/form-data, embedding directives that force Struts to generate temp files in /tmp or configured dirs.
2. Bypass Limits: Struts’ FileUploadInterceptor lacks strict bounds on file sizes or counts, allowing gigabytes of data to spill over.
3. Loop and Amplify: Using recursive actions or AJAX chains, requests multiply file creation, filling disks in minutes.
4. Trigger Crash: Once storage hits 100%, the JVM throws OutOfMemoryError or I/O exceptions, halting services.
5. Repeat for Persistence: Automated bots sustain the flood post-reboot.

Currently, tools like Burp Suite or custom scripts demonstrate PoC exploits consuming 90% disk space in under 5 minutes on a standard VPS.

Technical Deep Dive: Code Patterns Vulnerable to Exploitation

Vulnerable code in Struts 6.3.0 involves unpatched Commons-FileUpload integration:

<interceptor-ref name="fileUpload">
  <param name="maximumSize">25000000</param>  // Easily bypassed
</interceptor-ref>

The latest research from Apache indicates that without custom overrides, default configs allow unlimited stacking of temp blobs.

What Are the Potential Impacts of This Apache Struts Flaw on Businesses?

The Apache Struts disk exhaustion vulnerability can cripple online services, leading to downtime costing enterprises thousands per hour. A 2025 Ponemon Institute study estimates average DoS incident recovery at $8,500 per minute for mid-sized firms.

Key risks include:

• Service Outages: Websites, APIs, and internal portals go offline, alienating customers.
• Data Loss: Forced shutdowns corrupt logs and databases if not snapshotted.
• Reputation Damage: Public exploits amplify brand harm, as seen in 35% of Struts-using Fortune 500 firms.
• Chained Attacks: Disk full enables pivots to ransomware or lateral movement.

Real-World Examples and Statistics

In Q1 2025, Shodan scans revealed over 150,000 exposed Struts instances, 40% unpatched. Hypothetical attacks mirror the 2023 Log4Shell wave, where 20% of targets faced DoS floods.

Pros of Struts (MVC power, extensibility) are outweighed here by cons like legacy bloat increasing vuln surface.

How to Mitigate and Patch the Apache Struts Disk Exhaustion Vulnerability

Patching is the gold standard defense against CVE-2025-64775. Apache released Struts 6.4.0 in early 2026 with hardened FileUploadInterceptor limits and auto-cleanup.

Follow this numbered guide for secure remediation:

1. Assess Exposure: Scan with Nuclei or OWASP ZAP for CVE-2025-64775 signatures.
2. Upgrade Immediately: Migrate to Struts 6.4.1+; test in staging first.
3. Apply Workarounds: Set struts.multipart.maxSize=10MB in struts.xml.
4. Monitor Disk Usage: Deploy Prometheus alerts for >80% thresholds.
5. Harden Server: Use mod_security WAF rules to throttle multipart requests.
6. Conduct Pentest: Validate with ethical hackers quarterly.

Alternative Approaches: WAFs vs. Framework Switches

Web Application Firewalls (WAFs) like Cloudflare block 95% of exploits via regex on payloads. However, switching to Spring MVC or Jakarta EE reduces Struts-specific risks by 70%, per Gartner 2025 analysis.

• Pros of Patching: Quick, retains codebase.
• Cons: Regression risks in complex apps.
• Pros of Alternatives: Modern security baked-in.
• Cons: High migration costs (up to $500K for enterprises).

History of Apache Struts Vulnerabilities: Lessons from Past Flaws

Apache Struts has a storied vuln history, with over 200 CVEs since 2001. The 2017 Equifax hack via CVE-2017-5638 exposed 147M records, costing $1.4B.

Recent trends show DoS rising: 25% of 2024 Struts advisories targeted resource exhaustion.

Timeline of Key Apache Struts Security Issues

1. 2017: CVE-2017-5638 (RCE, 10/10 CVSS).
2. 2021: CVE-2021-31805 (OGNL injection).
3. 2024: Multiple XSS/DoS clusters.
4. 2025: CVE-2025-64775 (Disk DoS).

These connect via poor input sanitization themes, forming a knowledge graph of framework evolution needs.

Best Practices for Securing Web Frameworks Like Apache Struts

Beyond CVE-2025-64775, adopt zero-trust for frameworks: least privilege, auto-updates, and runtime protection.

In 2026, AI-driven scanners detect 85% more vulns pre-deploy, per Forrester.

• Enforce SBOMs for dependency tracking.
• Integrate SAST/DAST in CI/CD.
• Use containerization with seccomp profiles.

Comparing Struts to Modern Alternatives

Struts excels in legacy MVC but lags Spring Boot (fewer vulns, 2x faster patches).

Conclusion: Stay Ahead of Apache Struts Flaws

The CVE-2025-64775 Apache Struts flaw underscores the need for proactive security in Java web dev. By patching promptly, monitoring rigorously, and considering migrations, organizations can minimize disk exhaustion risks and ensure uptime.

With 60% of breaches starting from unpatched apps (Verizon DBIR 2025), vigilance is non-negotiable. Implement these strategies today for robust defense.

Frequently Asked Questions (FAQ) About Apache Struts Disk Exhaustion Vulnerability

What is CVE-2025-64775?

This is a disk exhaustion flaw in Apache Struts allowing unauthenticated DoS via temp file floods.

Which versions of Apache Struts are affected?

Struts 2.0 through 6.3.x; upgrade to 6.4.0+ for fixes.

How serious is the Apache Struts disk exhaustion attack?

CVSS 7.5 – high severity, potential for full outages in minutes.

Can WAFs stop this vulnerability?

Yes, rules blocking oversized multipart data mitigate 90-95% of attempts.

Is there a public exploit for CVE-2025-64775?

Proof-of-concepts exist on GitHub; expect weaponization soon.

What are signs of a disk exhaustion attack?

Sudden /tmp growth, JVM I/O errors, and 503 responses.

Should I replace Apache Struts entirely?

Not immediately, but evaluate Spring or Micronaut for long-term security.