CVE-2026-61550 in Icinga
Summary
by MITRE • 09/18/2026
Icinga 2 is an open source monitoring system. From 2.8 until 2.14.9, 2.15.4, and 2.16.2, certificate update JSON-RPC message handling does not validate that the sender is a trusted endpoint. An unauthenticated network attacker able to connect to TCP port 5665 can replace the node certificate and trusted CA certificate, impersonate a trusted node, and take control of the node. This issue is fixed in versions 2.14.9, 2.15.4, and 2.16.2.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified within Icinga 2 affects monitoring systems running version ranges from 2.8 through 2.14.8, as well as specific earlier releases of the 2.15 and 2.16 branches prior to their respective patched versions. This security flaw resides in the handling of certificate update JSON-RPC messages, which are critical for maintaining secure communication channels between distributed monitoring nodes. The core technical deficiency is a failure to validate the identity or trust status of the sender initiating these updates. In a properly secured environment, any request to modify cryptographic credentials must be authenticated and authorized by verifying that the source endpoint possesses valid certificates signed by a trusted Certificate Authority known to the system. However, in vulnerable versions, this validation step is absent, allowing any network actor with connectivity to TCP port 5665 to inject malicious certificate data without providing legitimate authentication credentials.
The operational impact of this flaw is severe and potentially catastrophic for infrastructure monitoring integrity. An unauthenticated attacker who can reach the Icinga 2 API endpoint on port 5665 can replace the node's own TLS certificate as well as the trusted Certificate Authority certificates stored by the system. By injecting a malicious CA certificate, the attacker effectively establishes themselves as a trusted entity within the cluster hierarchy. This allows them to impersonate legitimate monitoring nodes, intercept or modify monitored data streams, and potentially execute arbitrary commands if further exploitation vectors exist downstream. The ability to manipulate trust anchors undermines the fundamental security model of distributed monitoring systems, which rely on mutual TLS authentication to ensure that configuration changes and status updates originate from authorized sources only.
From a classification perspective, this vulnerability aligns with CWE-287 Improper Authentication, as the system fails to adequately verify the identity of an entity claiming access to critical resources. It also relates to CWE-345 Insufficient Verification of Data Authenticity, since the certificate update process does not confirm that the incoming data originates from a trusted source before accepting it into the security context. In terms of adversary behavior mapping under MITRE ATT&CK, this flaw facilitates techniques associated with Initial Access and Defense Evasion, specifically allowing an attacker to establish persistent access by manipulating trust relationships or impersonating legitimate services to bypass authentication mechanisms. The attack vector is classified as Network-based because exploitation requires network connectivity to the specific service port rather than local system access.
Mitigation strategies must prioritize immediate version upgrades for all affected systems. Administrators should upgrade Icinga 2 to version 2.14.9, 2.15.4, or 2.16.2 and later, where this validation logic has been corrected to ensure that only endpoints presenting valid certificates signed by a trusted CA can perform certificate updates. In environments where immediate patching is not feasible due to operational constraints, network-level controls should be implemented as compensating measures. This includes restricting access to TCP port 5665 using firewall rules or security groups so that it is accessible only from known and trusted IP addresses associated with legitimate monitoring nodes. Additionally, implementing strict TLS client certificate requirements for all API connections can help mitigate the risk by ensuring that even if validation logic is flawed, an attacker without a valid signed certificate cannot establish the necessary session to send malicious JSON-RPC messages. Regular auditing of certificate authorities and node configurations should also be conducted to detect any unauthorized changes promptly.