Executive brief
OPNsense is an open-source firewall and routing platform used to secure corporate and home networks. A security flaw in how the system handles DHCP configuration allows an administrative user to inject malicious commands into the underlying operating system. If exploited, an attacker could gain full control over the firewall, potentially leading to data interception, network disruption, or unauthorized access to the internal network.
Technical details
A command injection vulnerability exists in OPNsense versions prior to 26.1.8 within the DHCP interface configuration logic. The 'interface_dhcp_configure' function in 'src/etc/inc/interfaces.inc' fails to sanitize user-supplied input, such as the 'dhcphostname' or media parameters, before writing them to the dhclient configuration file. When the system executes the 'dhclient-script' shell script, these unsanitized values are processed in an 'eval' statement, leading to argument injection (CWE-88). An attacker with 'page-interfaces' privileges can exploit this to execute arbitrary commands as the root user. The issue is resolved in version 26.1.8.
Affected products
- OPNsense OPNsense < 26.1.8
Timeline
- 2026-05-12: advisory: Vendor advisory published via GitHub
- 2026-05-13: disclosed: NVD publication date