OpenNMS denial of service via XML entity expansion
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.
CVE-2026-111252
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-111252
Meridian
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Horizon
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://github.com/OpenNMS",
"vendor": "The OpenNMS Group",
"product": "Meridian",
"versions": [
{
"status": "affected",
"version": "2024.1.0",
"lessThan": "2024.3.14",
"versionType": "maven"
},
{
"status": "affected",
"version": "2025.0.0",
"lessThan": "2025.0.11",
"versionType": "maven"
},
{
"status": "affected",
"version": "2026.0.0",
"lessThan": "2026.0.1",
"versionType": "maven"
}
],
"defaultStatus": "unaffected"
},
{
"repo": "https://github.com/OpenNMS",
"vendor": "The OpenNMS Group",
"product": "Horizon",
"versions": [
{
"status": "affected",
"version": "36.0.0",
"lessThan": "36.0.5",
"versionType": "maven"
}
],
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-111252
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #34401 · Revision 1
- Added to Heist Feed
- Publisher date