CVE-2026-97359 in HFS2
Summary
by MITRE • 09/24/2026
HFS2 version 2.4.0 and earlier contains a template injection vulnerability in the multipart upload handler that allows unauthenticated attackers to achieve remote code execution by embedding malicious template syntax in a filename. Attackers can craft a filename containing a closing template quoting sequence followed by an exec macro, which bypasses the authorization check in the dispatcher to execute arbitrary commands on the underlying host system.
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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 server-side template injection flaw located within the multipart upload handler component of the application architecture. This specific weakness arises from insufficient input validation when processing filenames submitted during file uploads, allowing unauthenticated actors to inject malicious code directly into the rendering engine used by the web interface. The core technical failure lies in the dispatcher's authorization logic, which fails to properly sanitize or escape special characters within filename metadata before it is passed to the template parser. By embedding a closing template quoting sequence followed by an execution macro within the uploaded file name, attackers can effectively break out of the intended string context and inject arbitrary commands that are subsequently evaluated by the server-side engine. This mechanism bypasses standard authentication checks because the vulnerability exploits the internal processing pipeline rather than attempting to authenticate against user-facing login screens, thereby granting remote code execution capabilities on the underlying host system without any prior credentials or network-level access restrictions beyond basic HTTP connectivity.
From a technical perspective, this flaw aligns with CWE-94, commonly known as Improper Control of Generation of Code (Code Injection), specifically manifesting through server-side template injection techniques. The attack vector leverages the application's reliance on dynamic template rendering to display file listings or upload status messages. When an attacker uploads a file with a crafted name such as one containing closing delimiters and executable macros, the web server interprets these sequences not merely as data but as active code instructions. This leads to the execution of system-level commands under the privileges of the application process, which often runs with elevated permissions necessary for handling file operations. The impact is severe, as it allows complete compromise of the host operating system, enabling attackers to install backdoors, exfiltrate sensitive data, pivot to other internal network segments, or disrupt service availability through resource exhaustion attacks initiated via the same injection vector.
In terms of threat modeling and industry frameworks, this vulnerability maps directly to MITRE ATT&CK technique T1059, Command and Scripting Interpreter, specifically within the context of server-side execution environments like ASP.NET or similar web application stacks where HFS operates. The attack path corresponds to Initial Access via Web Applications (T1190) followed by Execution through command injection. Because the vulnerability is exploitable without authentication, it significantly lowers the barrier for entry, making it attractive to automated scanning tools and opportunistic attackers seeking quick system compromise on exposed web servers. The lack of input sanitization in the multipart upload handler highlights a fundamental design oversight where user-supplied data was treated as executable code rather than inert text during template rendering processes.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The most effective solution is to upgrade HFS to version 2.4.1 or later, where the developers have implemented proper input validation and output encoding mechanisms within the multipart upload handler to prevent template injection payloads from being processed as code. For environments where upgrading is not immediately feasible, administrators should restrict access to the web interface using network-level controls such as firewalls or reverse proxies that limit exposure to trusted IP addresses only. Additionally, implementing strict Content Security Policy headers and disabling unnecessary server-side features can reduce the attack surface. It is also critical to ensure that the application process runs with minimal privileges, adhering to the principle of least privilege, so that even if an injection occurs, the potential damage to the host system is contained. Regular security audits focusing on input validation across all user-facing endpoints are essential to prevent similar template injection vulnerabilities in other components of the web server infrastructure.