CVE-2026-19852 in NewSiteServer
Summary
by MITRE • 08/24/2026
NewSiteServer (NSS) developed by CyberTutor has an Arbitrary File Upload vulnerability. Unauthenticated remote attackers can upload arbitrary files, including malicious HTML files, thereby achieving effects similar to cross-site scripting.
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Analysis
by VulDB Data Team • 08/24/2026
The NewSiteServer application, developed by CyberTutor, contains a critical security flaw classified as an arbitrary file upload vulnerability. This weakness allows unauthenticated remote attackers to bypass authentication mechanisms and directly interact with the server's file handling subsystems without valid credentials. The core technical issue lies in insufficient validation of uploaded files, specifically regarding their type, content, and destination path. Because the application fails to enforce strict allowlists for permitted file extensions or verify MIME types against actual file signatures, it accepts a wide range of inputs that would typically be rejected by secure implementations. This lack of rigorous input sanitization creates an open channel for attackers to inject arbitrary data into the server's directory structure.
The operational impact of this vulnerability is severe due to its potential to facilitate cross-site scripting attacks and further system compromise. Attackers can upload malicious HTML files containing embedded JavaScript payloads, which are then served by the web server when accessed by other users or administrators. This effectively achieves a stored cross-site scripting effect without requiring direct code injection into database fields or user input forms that might have stricter validation rules. Beyond script execution, the ability to upload arbitrary files opens the door for remote code execution if an attacker can also control file names and paths to overwrite existing executable scripts or configuration files. In many web server configurations, uploaded HTML or PHP files may be executed by the backend interpreter, granting the attacker full command-line access equivalent to the user account under which the web service operates.
From a classification perspective, this vulnerability aligns with CWE-434, Unrestricted Upload of File with Dangerous Type, and CWE-79, Improper Neutralization of Input During Web Page Generation (Cross-site Scripting). The attack vector is categorized under MITRE ATT&CK technique T1505.002, Server-side web framework scripting, as it involves placing malicious scripts on the server to be executed later. Additionally, because the vulnerability allows unauthenticated access, it relates to CWE-306, Missing Authentication for Critical Function, indicating a fundamental failure in access control logic that should restrict file upload operations to authorized users only.
Mitigation strategies must address both the immediate technical flaw and broader architectural weaknesses. The most effective remediation is implementing strict server-side validation of uploaded files using an allowlist approach rather than denylists. This involves checking not just the file extension but also verifying the magic numbers or MIME types against expected values for legitimate content such as images or documents. Furthermore, uploaded files should be stored in a directory that does not have execute permissions and is separate from application code directories to prevent server-side execution of user-uploaded content. Renaming uploaded files with random strings can further mitigate path traversal risks. Access controls must also be enforced at the API level to ensure that only authenticated users with appropriate privileges can initiate file upload operations, thereby closing the unauthenticated access vector entirely.