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Introduction
A silent but devastating threat has emerged from deep inside one of the world’s most trusted web frameworks. Apache Struts, the backbone of countless enterprise applications, is facing a security storm that could bring entire infrastructures to a grinding halt. A newly identified flaw, cataloged as CVE-2025-64775, allows attackers to weaponize simple multipart requests and slowly bleed servers dry of disk space. What begins as a few unnoticed temporary files can evolve into total operational collapse. For businesses that rely on Struts, the revelation has triggered urgency, fear, and a scramble toward emergency patching.
Summary of the Original
A newly discovered security vulnerability in Apache Struts exposes organizations to disk exhaustion denial-of-service attacks that can bring entire systems to a standstill. Tracked as CVE-2025-64775, the issue lies within Apache Struts 2 due to improper handling of multipart requests. When users upload files through web forms, the framework processes the data by creating temporary files. A flaw in this cleanup process results in file leaks. Attackers can exploit this mechanism by sending maliciously crafted multipart requests that generate an overwhelming amount of temporary files, eventually consuming all available disk storage. Once a system runs out of space, it can no longer write logs or process data, leading to full denial of service.
Apache developers classify the vulnerability as “Important,” but organizations are urged to respond immediately. According to an advisory from Apache Struts developer Lukasz Lenart, the flaw affects many Struts versions across different branches. Reporter Nicolas Fournier identified the vulnerability, and no workaround currently exists, meaning configuration tweaks cannot mitigate the risk. The vulnerable ranges include Struts versions from 2.0.0 to 2.3.37, 2.5.0 to 2.5.33, 6.0.0 to 6.7.0, and 7.0.0 to 7.0.3.
Apache recommends upgrading to Struts 6.8.0 or later for the 6.x line, and 7.1.1 or later for the 7.x line. These updated releases maintain backward compatibility, ensuring smooth transitions for most environments. Organizations still running unsupported 2.3.x and 2.5.x versions face the greatest risk because these branches no longer receive security patches. Enterprises are advised to audit their systems, identify vulnerable deployments, coordinate upgrades across teams, and monitor for signs of attack such as rapid disk space depletion or failed write operations. Enhanced monitoring for unusual disk usage patterns can act as an early warning if exploitation occurs before patches are fully implemented.
The Full Story Behind the Struts Disk Exhaustion Crisis
A Hidden Weakness Inside a Trusted Framework
Apache Struts has earned its reputation through years of powering enterprise portals, financial systems, government web applications, and large-scale SaaS platforms. Its reliability has often been taken for granted. Yet this vulnerability shows how a seemingly small design flaw can create a catastrophic chain reaction. When multipart form uploads fail to clean up their temporary files, every request becomes a potential landmine, especially when automated by an attacker.
How Attackers Turn File Uploads Into Weapons
Multipart requests are a harmless part of everyday web activity. Photos, documents, spreadsheets, invoices, and profile updates all rely on this mechanism. Apache Struts processes these uploads by generating temporary working files before handing them off to the application. But in the vulnerable versions, these files remain on disk instead of being deleted. An attacker only needs to bombard the server with crafted multipart payloads. Every request silently leaves behind new files. Over minutes or hours, the accumulation grows until the system collapses.
Why Disk Exhaustion is Devastating for Enterprise Systems
Disk space is the lifeline for logs, transactions, cache storage, database writes, and session handling. When disks fill up unexpectedly, everything stops. Login functionality fails. APIs time out. Background jobs freeze. Even monitoring tools may stop logging issues because there is no space left to write error messages. Disk exhaustion is a shutdown mechanism that requires no advanced exploitation, no privilege escalation, and no code execution, making it a simple yet powerful attack vector.
The Scope of Vulnerability
The affected versions cover several generations of Struts. Two major branches, 2.3.x and 2.5.x, are already end-of-life and no longer patched. Organizations still running them are at the highest risk. Meanwhile, modern branches 6.x and 7.x also contain the flaw up to their listed versions. This widespread impact means enterprises across industries may be exposed.
Patching is the Only Defense
Apache’s advisory leaves no room for interim solutions. There is no configuration parameter that can disable multipart handling safely. There are no unofficial patches. Upgrade is the only path. Fortunately, Struts maintainers built backward compatibility into new releases to smooth the transition, limiting the risk of application breaks.
Why This Matters Now
In an era where threat actors automate attacks and scan the internet constantly for known vulnerabilities, the moment a CVE is published, global exploitation attempts are only hours away. Enterprises with outdated versions of Struts are now on borrowed time.
What Undercode Say
This vulnerability is dangerous because it transforms a basic web feature into a scalable DoS weapon without requiring deep technical expertise. The barrier to entry is low. Even amateur attackers with access to simple automation tools can generate enough multipart requests to overwhelm unsecured servers. Large enterprises must view this as more than a routine patch cycle. It is a wake-up call signaling the importance of modernizing legacy frameworks.
A disturbing trend continues to emerge across the cybersecurity landscape. Many businesses remain locked into older frameworks that are operationally critical but no longer supported. These legacy systems become blind spots. CVE-2025-64775 reinforces that unsupported versions are not just outdated, they are liabilities that invite exploitation. Attackers know that patching cycles are slow. This creates an asymmetry where defenders must scramble across multiple teams, while attackers only need a single open target to succeed.
The lack of a workaround is particularly telling. When a vulnerability has no mitigation path except upgrading, it signals an architectural flaw rather than a misconfiguration issue. The multipart handling system in older Struts versions is deeply embedded, making this vulnerability a structural weakness. It is not something administrators can patch at the filesystem or firewall level.
From a risk management standpoint, enterprises should consider implementing proactive disk monitoring across all applications, not just those using Struts. Disk exhaustion attacks have returned in various forms over recent years. Cloud environments add complexity because disk usage may grow dynamically, making attacks harder to detect until they reach critical levels.
The biggest lesson here is strategic technical debt management. Many organizations delayed upgrading to modern Struts versions because migrations can be complex across large distributed environments. Yet this incident highlights how delaying framework upgrades increases exposure. The financial and reputational cost of operational downtime often exceeds the cost of modernization.
CVE-2025-64775 also serves as a reminder that open-source ecosystems thrive on community vigilance. Reporter Nicolas Fournier’s discovery prevented a vulnerability that might have silently powered mass exploitation campaigns. Maintaining strong relationships with open-source communities, contributing back, and staying informed about advisories is essential for enterprise resilience.
Security teams should institutionalize a playbook for handling urgent framework vulnerabilities. This includes automated asset discovery, coordinated patch rollouts, and environment-wide monitoring. Organizations that rely heavily on Java-based frameworks should see this incident as justification for improving dependency management and adopting defense-in-depth strategies, especially around file handling operations.
🔍 Fact Checker Results
The vulnerability exists in multiple Apache Struts branches and has been formally confirmed. ✅
No workaround is available, and upgrading is the only solution. ✅
Disk exhaustion can lead to full denial of service, not partial degradation. ❌ (It results in total system unavailability, not limited disruption.)
📊 Prediction
Expect a surge in mass scanning activity targeting outdated Struts installations. 🌐
Organizations that delay upgrades may see proof-of-concept exploits circulating on underground forums. ⚠️
The incident may accelerate global migration efforts away from legacy Java frameworks. 🚀
🕵️📝✔️Let’s dive deep and fact‑check.
References:
Reported By: cyberpress.org
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