CVE-2026-19182 in Meridian
Summary
by MITRE • 08/13/2026
An incorrect authorization check in the v2 Alarm REST API in OpenNMS Meridian and Horizon allows a low-privileged authenticated user (ROLE_REST) to acknowledge, escalate, or clear alarms recorded as an arbitrary username, and, when also assigned ROLE_READONLY, to modify alarm state despite the read-only restriction. A credential check that should restrict these operations is guarded by an inverted condition, so it never executes for a real (non-blank) username. This can potentially allow an attacker to compromise the integrity of alarm state and audit records.
The solution is to upgrade to Meridian 2024.3.12, 2025.0.9 and Horizon 36.0.3 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.
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Analysis
by VulDB Data Team • 08/13/2026
The vulnerability described represents a critical authorization flaw in the v2 Alarm REST API of OpenNMS Meridian and Horizon platforms, specifically categorized as an improper access control issue under CWE-285. This weakness manifests as an inverted conditional logic error that fundamentally undermines the security model protecting alarm management operations. The flaw affects authenticated users with the ROLE_REST privilege level, creating a pathway for unauthorized manipulation of critical system events despite existing access controls designed to prevent such actions.
The technical implementation of this vulnerability stems from a logical inversion in the credential validation mechanism within the API endpoint responsible for alarm state modifications. When a user attempts to acknowledge, escalate, or clear alarms through the REST interface, the system should validate whether the operation is permitted for the specific username provided in the request. However, due to the inverted conditional statement, this validation never executes when a legitimate (non-blank) username is present, effectively bypassing authorization checks entirely. This condition creates a scenario where any user with ROLE_REST can perform administrative operations on alarms as if they were acting under any arbitrary username identity.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass data integrity compromise and audit trail manipulation. When combined with the ROLE_READONLY assignment, attackers can exploit the flaw to modify alarm states despite apparent read-only restrictions, creating a dangerous situation where system administrators cannot trust the accuracy of their alarm management records. This represents a significant threat to operational security since alarm systems serve as critical monitoring tools for detecting and responding to system failures, security incidents, and performance degradation events.
The vulnerability directly relates to ATT&CK technique T1548.001 which covers privilege escalation through abuse of credentials, and T1562.008 which addresses data destruction through manipulation of audit logs. The flaw enables attackers to compromise the integrity of alarm state information that forms part of the system's security monitoring infrastructure, potentially masking malicious activities or creating false positives that could distract security teams from actual threats. This type of vulnerability is particularly dangerous in enterprise environments where OpenNMS serves as a central monitoring platform for network infrastructure and application health.
Organizations affected by this vulnerability should immediately implement the recommended remediation measures by upgrading to Meridian 2024.3.12, 2025.0.9 or Horizon 36.0.3 and newer versions, which contain the necessary code fixes to correct the inverted conditional logic. Security teams should also consider implementing additional monitoring for unauthorized alarm manipulation attempts, particularly focusing on unusual patterns of alarm acknowledgments or state changes that could indicate exploitation of this vulnerability. The security advisory emphasizes that these platforms are intended for private network deployment and should not be directly exposed to internet-facing services, as this exposure increases the attack surface and potential impact of such authorization bypass vulnerabilities.
The root cause analysis reveals that this vulnerability represents a classic example of insecure programming practices in API development where conditional logic errors can create fundamental security weaknesses. The fix implemented in the updated versions addresses the core issue by correcting the inverted conditional statement to properly validate credentials before executing privileged operations. This correction ensures that alarm management operations are properly restricted based on the authenticated user's actual permissions and identity, restoring the intended security model for the OpenNMS platform's monitoring capabilities.
Organizations should conduct comprehensive vulnerability assessments to identify any potential exploitation of this flaw within their existing deployments, particularly focusing on systems where users have been granted ROLE_REST privileges. The remediation process should include not only software updates but also verification that no unauthorized modifications to alarm records occurred during the period when the vulnerability was present. Additionally, security teams should review their overall access control policies to ensure that users are granted appropriate privilege levels and that the principle of least privilege is properly enforced across all OpenNMS components. The vulnerability serves as a reminder of the critical importance of thorough code review processes for authentication and authorization logic in enterprise security platforms where the integrity of monitoring data directly impacts organizational security posture.