VulnerabilityPublished 13 Aug 2026

CVE-2026-19182: The OpenNMS Group Meridian · Incorrect Authorization

Affects The OpenNMS Group MeridianSource CVE Database V5

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Not known to be exploited · CVSS 4.3 Medium : upgrade to 2025.0.9 or 2024.3.12 when convenient.

Data as of 11 Nov 2026, 23:24 UTC

CVSS 3.1 base score

4.3Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 17% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2025.0.9, 2024.3.12, 36.0.3

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

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

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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 11 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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.

ghsa-r53w-fffc-9ppv

What to do

Upgrade Meridian to 2025.0.9 or 2024.3.12; Horizon to 36.0.3.

Affected software

Product	Affected	Fixed in
The OpenNMS GroupMeridian	Affected >=2025.0.0 <2025.0.9	Fixed in 2025.0.9
The OpenNMS GroupMeridian	Affected >=2024.1.0 <2024.3.12	Fixed in 2024.3.12
The OpenNMS GroupHorizon	Affected >=36.0.0 <36.0.3	Fixed in 36.0.3
GitHubMeridian`pkg:github/Meridian`Other threats	Affected >=2024.1.0 <2024.3.12 >=2025.0.0 <2025.0.9	Fixed in 2024.3.12 2025.0.9
GitHubHorizon`pkg:github/Horizon`Other threats	Affected >=36.0.0 <36.0.3	Fixed in 36.0.3

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

AI-suggested

A fix is available by upgrading to Meridian 2024.3.12, 2025.0.9, or Horizon 36.0.3 or newer. Organizations should apply these updates promptly. Additionally, since these products are intended for private network use, ensure they are not directly accessible from the Internet to reduce exposure risk.

Description

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.

Impact

The vulnerability allows unauthorized modification of alarm states and audit records by low-privileged authenticated users, potentially compromising the integrity of alarm management and audit data. There is no impact on confidentiality or availability reported. The CVSS score is 4.3 (medium severity), reflecting limited impact confined to integrity with no elevation of privileges or denial of service.

Summary

This vulnerability (CVE-2026-19182) in OpenNMS Meridian and Horizon arises from an incorrect authorization check in the v2 Alarm REST API. A low-privileged authenticated user with ROLE_REST can perform alarm state changes (acknowledge, escalate, clear) under arbitrary usernames. When combined with ROLE_READONLY, the user can modify alarm states despite supposed read-only restrictions. The root cause is an inverted condition in the credential check that prevents proper enforcement for non-blank usernames. This flaw can undermine the integrity of alarm states and audit trails. The vulnerability affects Meridian versions 2024.1.0 and 2025.0.0 and Horizon 36.0.0, specifically versions before Meridian 2024.3.12 and 2025.0.9, and Horizon 36.0.3. The vendor advises upgrading to these versions to remediate the issue. The products are designed for private network deployment and should not be exposed to the Internet.

CWE-863Incorrect Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #17OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
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)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/OpenNMS/opennms/pull/8755 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Aug 2026, 05:30 UTC

WeaknessesCWE-863

Technical details

References

Community reviews

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