CVE-2026-97362 in HFS2
Summary
by MITRE • 09/24/2026
HFS2 version 2.4.0 and earlier contains a denial of service vulnerability that allows unauthenticated attackers to cause a complete and persistent loss of availability by sending a single crafted request. Attackers can trigger a hung serving thread that enters a busy loop, rendering the entire file server unresponsive to all clients without self-recovery until an operator manually restarts the service.
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Analysis
by VulDB Data Team • 09/24/2026
The vulnerability identified in HFS version 2.4.0 and earlier represents a critical denial of service flaw rooted in improper input validation and resource management within the web server's request handling logic. This specific weakness allows unauthenticated remote attackers to disrupt the availability of the file sharing service with minimal effort, requiring only a single crafted HTTP request to initiate the attack vector. The core technical issue lies in how the application processes certain malformed or specifically constructed inputs that trigger an infinite loop condition within one of its serving threads. Instead of gracefully handling invalid data or timing out appropriately, the server enters a busy wait state where it continuously consumes CPU cycles without making progress on other tasks or releasing system resources associated with that thread.
From a technical perspective, this behavior classifies as CWE-835, which describes loops that consume excessive processing time due to missing exit conditions or incorrect boundary checks. The vulnerability exploits the synchronous nature of many traditional web server architectures where each incoming connection is handled by a dedicated thread or process. When an attacker sends the malicious payload, it causes one of these threads to become permanently stuck in a computational loop. Because the operating system scheduler continues to allocate CPU time to this hung thread, and because the application may have limited concurrency limits or fail to properly isolate faulty requests from healthy ones, the entire server instance becomes effectively paralyzed. The service does not exhibit self-healing properties; it cannot recover from this state automatically, necessitating manual intervention by a system administrator to terminate the stuck process and restart the HFS service entirely.
The operational impact of this vulnerability is severe for any organization relying on HFS for file distribution or internal data sharing. Since the attack requires no authentication, it can be executed by anyone with network access to the target server, including external threat actors scanning for vulnerable instances. The resulting denial of service leads to a complete loss of availability for all legitimate users attempting to access files through the interface. This persistent outage disrupts business operations that depend on timely file retrieval and creates significant administrative overhead due to the need for manual recovery procedures. In environments where high availability is critical, such as corporate intranets or public-facing download portals, this flaw can lead to substantial productivity losses and potential reputational damage if not addressed promptly.
To mitigate this risk, organizations running HFS version 2.4.0 or earlier should prioritize upgrading to a patched version that addresses the underlying loop condition in the request parser. If immediate patching is not feasible, deploying a web application firewall can help by inspecting incoming traffic for patterns characteristic of this exploit and blocking them before they reach the vulnerable server logic. Additionally, implementing network-level rate limiting and connection timeouts can reduce the likelihood of successful exploitation by restricting how quickly requests are processed or terminating connections that appear to be engaging in abusive behavior. Monitoring system resources such as CPU usage per process can also aid in early detection of such attacks, allowing administrators to respond before a complete service outage occurs. This vulnerability aligns with ATT&CK technique T1499, Endpoint Denial of Service, specifically under the sub-technique for resource exhaustion via application layer flooding or logic exploitation.