CVE-2026-33218 (GCVE-0-2026-33218)
Vulnerability from cvelistv5 – Published: 2026-03-25 19:53 – Updated: 2026-03-25 19:53
VLAI?
Title
NATS has pre-auth server panic via leafnode handling
Summary
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. 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.
Severity ?
7.5 (High)
CWE
- CWE-20 - Improper Input Validation
Assigner
References
| URL | Tags | |||||||
|---|---|---|---|---|---|---|---|---|
|
||||||||
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| nats-io | nats-server |
Affected:
< < 2.11.15
Affected: >= 2.12.0-RC.1, < 2.12.6 |
{
"containers": {
"cna": {
"affected": [
{
"product": "nats-server",
"vendor": "nats-io",
"versions": [
{
"status": "affected",
"version": "\u003c \u003c 2.11.15"
},
{
"status": "affected",
"version": "\u003e= 2.12.0-RC.1, \u003c 2.12.6"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. 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."
}
],
"metrics": [
{
"cvssV3_1": {
"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"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-20",
"description": "CWE-20: Improper Input Validation",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-03-25T19:53:12.075Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339"
},
{
"name": "https://advisories.nats.io/CVE/secnote-2026-10.txt",
"tags": [
"x_refsource_MISC"
],
"url": "https://advisories.nats.io/CVE/secnote-2026-10.txt"
}
],
"source": {
"advisory": "GHSA-vprv-35vv-q339",
"discovery": "UNKNOWN"
},
"title": "NATS has pre-auth server panic via leafnode handling"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-33218",
"datePublished": "2026-03-25T19:53:12.075Z",
"dateReserved": "2026-03-17T23:23:58.314Z",
"dateUpdated": "2026-03-25T19:53:12.075Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2026-33218\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-03-25T20:16:32.623\",\"lastModified\":\"2026-03-25T20:16:32.623\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. 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.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-20\"}]}],\"references\":[{\"url\":\"https://advisories.nats.io/CVE/secnote-2026-10.txt\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339\",\"source\":\"security-advisories@github.com\"}]}}"
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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