CVE-2026-1791 in Operation and Maintenance Security Gateway
Summary
by MITRE • 02/04/2026
Unrestricted Upload of File with Dangerous Type vulnerability in Hillstone Networks Operation and Maintenance Security Gateway on Linux allows Upload a Web Shell to a Web Server.This issue affects Operation and Maintenance Security Gateway: V5.5ST00001B113.
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Analysis
by VulDB Data Team • 02/05/2026
The vulnerability identified as CVE-2026-1791 represents a critical security flaw in Hillstone Networks Operation and Maintenance Security Gateway version 5.5ST00001B113, specifically impacting the Linux-based web server component. This issue constitutes an unrestricted file upload vulnerability that allows authenticated attackers to bypass security controls and upload malicious files to the system. The flaw specifically permits the upload of files with dangerous types, creating a significant attack surface that can be exploited to gain unauthorized access to the underlying system. The vulnerability stems from inadequate validation mechanisms within the file upload functionality, which fails to properly restrict file types or implement proper sanitization checks before accepting and storing uploaded content. This type of vulnerability is particularly dangerous because it directly enables remote code execution capabilities through web shell deployment, allowing attackers to establish persistent access to the compromised system.
The technical implementation of this vulnerability aligns with CWE-434, which describes the weakness of unrestricted upload of file with dangerous type, and represents a direct violation of secure coding practices for file handling operations. The flaw exists in the web server component of the security gateway, where the application fails to enforce proper file type validation or content inspection before storing uploaded files. Attackers can exploit this by uploading malicious web shell files that are subsequently executed by the web server, providing them with a command execution interface on the target system. The vulnerability affects the operational maintenance interface of the security gateway, which typically requires administrative privileges to access, making the potential impact even more severe as attackers can leverage legitimate administrative access points to deploy their payloads. This weakness directly enables the ATT&CK technique T1190 - Exploit Public-Facing Application, where adversaries target web applications to establish initial access and subsequently escalate privileges through the uploaded malicious content.
The operational impact of this vulnerability extends beyond simple unauthorized file uploads, as it creates a persistent backdoor that can be used for reconnaissance, lateral movement, and data exfiltration within the network. Once a web shell is successfully uploaded and executed, attackers can perform various malicious activities including but not limited to system enumeration, privilege escalation, and establishing covert communication channels. The vulnerability affects the core security gateway functionality, potentially compromising the integrity of network security policies and allowing attackers to bypass firewall rules, intrusion detection systems, and other security controls implemented by the device. Organizations relying on this specific version of the Hillstone security gateway face significant risk of unauthorized access to their network infrastructure, as the vulnerability can be exploited remotely without requiring advanced technical skills or specialized tools. The impact is particularly severe for environments where these gateways serve as primary security controls, as successful exploitation could lead to complete compromise of the protected network segments.
Mitigation strategies for CVE-2026-1791 must address both immediate remediation and long-term security hardening measures. Organizations should prioritize applying the vendor-supplied patches or firmware updates that address this specific vulnerability, as Hillstone is likely to have released security fixes for this issue. Network administrators should implement strict file type validation and content inspection mechanisms, ensuring that all uploaded files undergo thorough analysis before acceptance. The principle of least privilege should be enforced by restricting upload capabilities to only authorized administrative users and implementing additional authentication layers. Security monitoring should be enhanced to detect unusual file upload patterns or suspicious file types that may indicate exploitation attempts. Additionally, network segmentation and access control policies should be reviewed to limit the potential impact of successful exploitation. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other network components, while implementing proper input validation and output encoding techniques to prevent similar issues in future development cycles. The vulnerability serves as a reminder of the critical importance of secure file handling practices and proper validation of user-supplied content in network security devices.