Answer in brief
CVE-2026-111252 records a Medium severity (CVSS 6.5) vulnerability in OpenNMS denial of service via XML entity expansion. The current sources do not mark it as known exploited. The current feed maps The OpenNMS Group/Horizon (generic), The OpenNMS Group/Meridian (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps The OpenNMS Group/Horizon (generic), The OpenNMS Group/Meridian (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| The OpenNMS Group/Horizongeneric | >=36.0.0 <36.0.5 | 36.0.5 |
| The OpenNMS Group/Meridiangeneric | >=2024.1.0 <2024.3.14 || >=2025.0.0 <2025.0.11 || >=2026.0.0 <2026.0.1 | 2024.3.14, 2025.0.11, 2026.0.1 |
Published upstream
Oct 15, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 15, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Oct 15, 2026
A denial of service vulnerability exists in the XML parsing of multiple versions of OpenNMS Meridian and Horizon. OpenNMS parsed XML without an effective limit on entity expansion. A document with a DOCTYPE that declares internal entities can expand to a very large value and exhaust the server memory. An authenticated user with provisioning access can supply such a document through a requisition or foreign-source import, which includes a remote requisition URL that the server fetches and parses. Both deeply nested entities and a single large entity referenced many times cause the memory exhaustion. The fix caps the number of entity expansions for all XML parsing and rejects any DOCTYPE in requisition and foreign-source XML. The 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.
Quoted source text, attributed separately from HOL analysis.