CVE-2019-25370 in OPNsense
Summary
by MITRE • 02/15/2026
OPNsense 19.1 contains a reflected cross-site scripting vulnerability that allows attackers to inject malicious scripts by submitting crafted input through multiple parameters. Attackers can send POST requests to interfaces_vlan_edit.php with script payloads in the tag, descr, or vlanif parameters to execute arbitrary JavaScript in users' browsers.
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Analysis
by VulDB Data Team • 02/20/2026
The vulnerability identified as CVE-2019-25370 represents a critical reflected cross-site scripting flaw within OPNsense version 19.1, specifically affecting the interfaces_vlan_edit.php web interface component. This vulnerability stems from insufficient input validation and output encoding mechanisms that fail to properly sanitize user-supplied data before rendering it within web responses. The flaw exists in the handling of multiple HTTP parameters including tag, descr, and vlanif, which are processed without adequate sanitization measures that would prevent malicious script execution. The vulnerability is classified under CWE-79 as a failure to sanitize input, making it susceptible to XSS attacks that can compromise user sessions and execute unauthorized commands.
The technical exploitation of this vulnerability requires attackers to craft malicious POST requests targeting the interfaces_vlan_edit.php endpoint with specially formatted payloads containing JavaScript code within the vulnerable parameters. When legitimate users interact with the affected interface, their browsers execute the injected scripts within the context of the vulnerable application, potentially leading to session hijacking, credential theft, or unauthorized administrative actions. The reflected nature of this vulnerability means that malicious input is immediately reflected back to the user's browser without being stored, making it particularly dangerous for targeted attacks. This vulnerability aligns with ATT&CK technique T1566.001 for credential access through spearphishing attachments and T1059.007 for scripting through web applications, as it enables attackers to execute arbitrary code within user browsers.
The operational impact of CVE-2019-25370 extends beyond simple script execution, as it can enable attackers to establish persistent access to network management interfaces and potentially escalate privileges within the OPNsense environment. Attackers can leverage this vulnerability to steal administrative credentials, modify network configurations, or establish backdoors through the compromised management interface. The vulnerability affects the core network infrastructure management capabilities of OPNsense, potentially compromising the security posture of entire networks that rely on this firewall solution. Organizations using affected versions face significant risk of unauthorized access to their network infrastructure, particularly in environments where administrative access to OPNsense is required for network management tasks.
Mitigation strategies for this vulnerability should include immediate patching to OPNsense version 19.1.11 or later, which contains the necessary fixes for input validation and output encoding. Network administrators should also implement additional security controls such as web application firewalls, input validation rules, and regular security assessments of web interfaces. The implementation of Content Security Policy headers can provide additional protection against XSS attacks by restricting script execution within the application context. Organizations should conduct comprehensive security audits of their OPNsense installations to identify other potential vulnerabilities and ensure proper network segmentation to limit the impact of potential exploitation. Regular monitoring of system logs for suspicious activity and implementing multi-factor authentication for administrative access can further reduce the risk associated with this vulnerability. The vulnerability demonstrates the importance of proper input validation and output encoding practices as outlined in OWASP Top 10 2017 category A03: Sensitive Data Exposure, where inadequate sanitization of user inputs creates dangerous conditions for cross-site scripting attacks.