VulnerabilityPublished 10 Sep 2026

CVE-2026-89054: The OpenNMS Group Horizon · Missing Authorization

Affects The OpenNMS Group HorizonSource CVE Database V5

Not known to be exploited · CVSS 8.2 High : upgrade to 36.0.4 soon.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

8.2High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.5% chance of exploitation in 30 days – higher than 43% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 36.0.4

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade The OpenNMS Group Horizon to 36.0.4.

Affected software

Product	Affected	Fixed in
The OpenNMS GroupHorizon	Affected >=36.0.0 <36.0.4	Fixed in 36.0.4
GitHubHorizon`pkg:github/Horizon`Other threats	Affected >=36.0.0 <36.0.4	Fixed in 36.0.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade to OpenNMS Horizon version 36.0.4 or newer, where the missing authorization on PATCH methods has been fixed. Additionally, ensure that Horizon installations are deployed within private networks and are not directly accessible from the Internet, as recommended by the vendor. Patch status is confirmed by the vendor advisory specifying the fix in version 36.0.4.

Description

A missing authorization vulnerability in OpenNMS Horizon allows configuration changes without authentication. The Spring Security policy for the /api/v2 REST API defines authorization rules for every HTTP method except PATCH, so the shipped @PATCH configuration endpoints for event configuration and SNMP data collection (which enable and disable event definitions and data-collection sources) are reachable with no authorization enforced. An unauthenticated attacker able to reach the web UI can disable event definitions and SNMP data collection, suppressing event and alarm generation and stopping metric collection - silently degrading monitoring and detection - with the change persisted and reloaded into the running system. The solution is to upgrade to Horizon 36.0.4 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.

Impact

An unauthenticated attacker with access to the web UI can disable event definitions and SNMP data collection, which suppresses event and alarm generation and stops metric collection. This results in silent degradation of monitoring and detection capabilities, potentially allowing malicious activity or system failures to go unnoticed. The integrity of monitoring data is impacted, but confidentiality is not affected. Availability impact is low as the system continues running but with reduced monitoring functionality.

Summary

OpenNMS Horizon contains a missing authorization vulnerability (CWE-862) in its /api/v2 REST API where PATCH HTTP methods lack authorization enforcement. This affects endpoints related to event configuration and SNMP data collection, allowing unauthenticated attackers who can reach the web UI to disable critical monitoring functions. The changes persist and reload into the running system, causing silent degradation of monitoring and detection capabilities. The vulnerability affects versions >=36.0.0 and <36.0.4. The vendor has addressed this issue in version 36.0.4. The product is designed for private network use and should not be exposed to the Internet.

CWE-862Missing Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #4OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
Attack patterns
Exploitation of Thunderbolt Protection Flaws (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/OpenNMS/opennms/pull/8833 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Sep 2026, 20:01 UTC

WeaknessesCWE-862

Technical details

References

Community reviews

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