CVE-2026-33218

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Prior to versions 2.11.15 and 2.12.6, a client which can connect to the leafnode port can crash the nats-server with a certain malformed message pre-authentication. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable leafnode support if not needed or restrict network connections to the leafnode port, if plausible without compromising the service offered."}, {"lang": "es", "value": "NATS-Server es un servidor de alto rendimiento para NATS.io, un sistema de mensajer\u00eda nativo de la nube y del borde. Antes de las versiones 2.11.15 y 2.12.6, un cliente que puede conectarse al puerto leafnode puede bloquear el nats-server con un mensaje malformado espec\u00edfico pre-autenticaci\u00f3n. Las versiones 2.11.15 y 2.12.6 contienen una correcci\u00f3n. Como soluci\u00f3n alternativa, deshabilite el soporte de leafnode si no es necesario o restrinja las conexiones de red al puerto leafnode, si es factible sin comprometer el servicio ofrecido."}], "id": "CVE-2026-33218", "lastModified": "2026-09-09T13:19:23.977", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-33218", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-03-26T15:37:53.583818Z", "version": "2.0.3"}}]}, "published": "2026-03-25T20:16:32.623", "references": [{"source": "security-advisories@github.com", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://advisories.nats.io/CVE/secnote-2026-10.txt"}, {"source": "security-advisories@github.com", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:21769"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:22347"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:23345"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/security/cve/CVE-2026-33218"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2451450"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33218.json"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-20"}], "source": "security-advisories@github.com", "type": "Secondary"}, {"description": [{"lang": "en", "value": "CWE-1286"}], "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "type": "Secondary"}]}

{"bugzilla": {"description": "nats-server: github.com/nats-io/nats-server: NATS-Server: Denial of Service via malformed message pre-authentication on leafnode port", "id": "2451450", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2451450"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-1286", "details": ["A flaw was found in NATS-Server, a high-performance messaging system. A remote attacker, by connecting to the leafnode port and sending a specially crafted malformed message before authentication, can cause the nats-server to crash. This vulnerability leads to a Denial of Service (DoS), making the server unavailable to legitimate users."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability."}, "name": "CVE-2026-33218", "package_state": [{"cpe": "cpe:/a:redhat:multicluster_globalhub", "fix_state": "Affected", "package_name": "multicluster-globalhub/multicluster-globalhub-grafana-rhel9", "product_name": "Multicluster Global Hub"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Affected", "package_name": "openshift4/oc-mirror-plugin-rhel9", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-03-25T19:53:12Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-33218\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-33218\nhttps://advisories.nats.io/CVE/secnote-2026-10.txt\nhttps://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339"], "threat_severity": "Important"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,2.11.15)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[2.12.0-RC.1,2.12.6)"}}], "enrichment": {"confidence": 91.0, "confidence_source": "matching", "scores": [{"score": 91.0, "source": "matching"}]}, "original": {"product": "nats-server", "source": "cna", "vendor": "nats-io"}, "product": "nats_server", "vendor": "nats"}], "analysis": {"en": {"generated_at": "2026-03-26T18:55:02.073891+00:00", "value": {"mitigation_remediation": ["Upgrade NATS-Server to version 2.11.15 or later 2.12.6 to apply the vendor fix.", "If an upgrade is not immediately possible, disable the leafnode feature in the server configuration to eliminate the vulnerable code path.", "As an additional safeguard, restrict network access to the leafnode port through firewalls or network segmentation to limit exposure."], "summary": {"action": "Apply Patch", "impact": "Denial of Service"}, "threat_synthesis": {"affected_systems": "All NATS\u2011IO NATS\u2011Server releases prior to 2.11.15 and 2.12.6 are vulnerable; any client that can connect to the leafnode port jeopardizes the system. The vulnerability impacts only the server process and does not compromise data confidentiality or integrity.", "description_and_impact": "A malformed message sent to the leafnode port of NATS-Server causes a pre-authentication crash that can terminate the service. The denial of service can be triggered by any network actor that can reach the leafnode interface, without authentication, resulting in loss of availability for all connected clients. The issue arises from improper input handling and an unguarded panic path (CWE\u201120 and CWE\u20111286).", "risk_and_exploitability": "The CVSS score of 7.5 designates this as a high severity flaw, while an EPSS score of less than one percent indicates that exploitation is currently uncommon. It is not listed in the CISA KEV catalog. Because the leafnode port is a network-facing endpoint, an attacker who can reach it can trigger the crash immediately, with no authentication or additional privileges required. The threat is mitigated by disabling leafnode support or restricting network access to the port."}}}}, "created": "2026-03-25T21:46:21.150572+00:00", "updated": "2026-03-27T09:30:11.871845+00:00", "vendors": ["nats", "nats$PRODUCT$nats_server"]}