{"id":"CVE-2026-111235","published":"2026-10-15T19:17:36.693","lastModified":"2026-10-16T20:17:19.620","description":"An authorization bypass vulnerability exists in the REST API of multiple versions of OpenNMS Meridian and Horizon. The /rest/** Spring Security filter chains authorize requests with intercept-url rules that name the HTTP method as an uppercase token, compare the method case-sensitively, and have no terminal deny rule. A request that uses a non-canonical (for example lowercase) method token matches no rule and is processed without authentication. A remote, unauthenticated attacker can read the monitored inventory and can create, modify, or delete resources through the REST API, which includes injecting events to fabricate or suppress alarms. The /rest/alarms chain has the same missing deny rule and discloses whether an alarm exists through a difference in the response. The fix adds a terminal deny rule to each REST filter chain.\n\n\n\nThe solution is to upgrade to Meridian 2024.3.14, 2025.0.11, 2026.0.1 and Horizon 36.0.5 or newer. Meridian and Horizon installation instructions state that they are intended for installation within an organization's private networks and should not be directly accessible from the Internet.","cvssScore":9.1,"cvssSeverity":"CRITICAL","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","cwes":["CWE-204","CWE-862","CWE-863"],"vendors":[],"products":[],"references":[{"url":"https://github.com/OpenNMS/opennms/pull/8934","tags":[]}],"exploitRefs":[{"url":"https://github.com/OpenNMS/opennms/pull/8934","tags":[]}],"hasPoc":true,"ai":{"summary":"An authorization bypass vulnerability in OpenNMS Meridian and Horizon allows unauthenticated attackers to access REST API endpoints that should require authentication, enabling them to read monitored inventory and manipulate resources including alarms. This critical flaw occurs because HTTP method case-sensitive matching fails to include a terminal deny rule for non-canonical method names.","exploitability":"Exploitation is straightforward for remote attackers with no prerequisites, as the vulnerability allows bypassing authentication using lowercase HTTP methods that match no authorization rules.","blast_radius":"The impact could be significant in environments where OpenNMS is exposed to untrusted networks, allowing attackers to manipulate monitoring data, suppress alarms, and potentially disrupt operational visibility.","remediation":"Upgrade to Meridian 2024.3.14, 2025.0.11, 2026.0.1 or Horizon 36.0.5 or newer immediately.","detection":"No reliable host or network indicator is derivable from the published description.","tags":["auth-bypass","rest-api","monitoring","network"],"model":"garnet-coder","analyzedAt":"2026-10-16T08:48:52.795Z"}}