CVE-2026-86427

LibreNMS before 26.3.1 contains a stored cross-site scripting vulnerability in legacy PHP templates that output SNMP-sourced and syslog-sourced data without escaping. An attacker who controls a monitored network device can inject arbitrary JavaScript through SNMP interface descriptions or syslog program fields that executes when authenticated users view affected pages.

LibreNMS before 26.5.0 contains stored cross-site scripting vulnerabilities in VRF display pages where mplsVpnVrfDescription, vrf_name, and mplsVpnVrfRouteDistinguisher fields from SNMP polling are rendered without sanitization. Attackers controlling a monitored network device can inject arbitrary JavaScript through SNMP responses that executes in the browser of any user viewing VRF-related pages.

LibreNMS versions before 26.5.0 contain a remote code execution vulnerability in the AboutController where the snmpget configuration parameter is passed to shell_exec() without proper validation. An authenticated administrator can modify the snmpget configuration to point to a malicious executable file and trigger code execution by accessing the /about endpoint.

LibreNMS before version 26.8.0 contains an authentication bypass vulnerability in the REST API that allows unauthenticated attackers to access protected endpoints by sending numeric values instead of string tokens. Attackers can exploit MySQL type coercion by sending small integers like 0 through 9 to match token hashes, gaining access to API functionality including device credentials and administrative features that enable remote code execution through alert templates.

LibreNMS before 24.10.0 allows a remote attacker to execute arbitrary code via OS command injection involving AboutController.php's index(), SettingsController.php's update(), and PollDevice.php's initRrdDirectory().

LibreNMS versions >= 23.10.0 and < 26.2.0 (fixed in 26.4.0) contain an authenticated OS command injection vulnerability in libvirt discovery. When libvirt support is enabled (enable_libvirt=true), the device hostname ($this->getDevice()->hostname) is concatenated into shell commands (ssh, virsh list/dumpxml/domstate) in VminfoLibvirt.php and passed to exec() without escapeshellarg() or argument separation. An authenticated admin can set a crafted device hostname to inject arbitrary OS commands, leading to remote code execution in the discovery worker context.

LibreNMS through 26.2.0 contains a stored cross-site scripting vulnerability in legacy PHP template pages that render unescaped SNMP-sourced data fields including BGP peer descriptions, VRF names, process information, and SLA tags. Attackers with device management access or network access to enroll a rogue SNMP device can inject malicious JavaScript that executes when admins view affected routing and device pages, enabling credential theft and CSRF token exfiltration.

LibreNMS through 26.4.0 renders JSON fields (name, ip, model, author, commit message) returned by the admin-configurable Oxidized integration URL (oxidized.url) into the device showconfig page without applying htmlspecialchars(). An administrator who points the Oxidized URL at an attacker-controlled server (SSRF) can cause it to return malicious JSON, resulting in stored/persistent cross-site scripting affecting all users who view any device's showconfig tab. Fixed in 26.7.0.

LibreNMS versions <= 26.4.0 contain a stored cross-site scripting vulnerability in the graph_descr.<graphtype> configuration settings, which are echoed verbatim without HTML escaping in includes/html/pages/graphs.inc.php. An administrator can store a malicious HTML payload that executes in the browser of any authenticated user who views the affected graph type. The issue is fixed in version 26.7.0.

LibreNMS versions from 21.6.0 up to 26.5.0 are vulnerable to command injection in the Signal alert transport because the signal-cli path and the Recipient field are insufficiently escaped before being passed to an exec call. An authenticated administrator can execute arbitrary OS commands on the LibreNMS host.