High
nats-server — security advisory
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.
- Products
- nats-server
- Affected versions
- 2.10.24-1, 2.10.27-1, 2.10.27-1build1, 2.10.27-1ubuntu0.26.04.1~esm1, 2.10.3-1, 2.10.4-1, 2.10.7-1, 2.10.7-1ubuntu0.1, 2.10.7-1ubuntu0.2, 2.10.7-1ubuntu0.3, 2.14.1-1, 2.14.3-1, 2.9.19-1build1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-27889
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 00:56 UTC · Revision 1
Source evidence
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.
osv:UBUNTU-CVE-2026-27889
nats-server
Fixed versions: Not specified
nats-server
Fixed versions: Not specified
nats-server
Fixed versions: Not specified
nats-server
Fixed versions: Not specified
Complete source record
{
"id": "177f594a10d235260d35b661f4671e289ccbc96c401521e4ce8f9c30ebd51f98",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-27889",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-27889",
"summary": "NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.",
"evidence": "osv:UBUNTU-CVE-2026-27889",
"products": [
{
"name": {
"value": "nats-server",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.9.19-1build1",
"evidence": "/affected/0/versions"
},
{
"value": "2.10.3-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.10.4-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.10.7-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.10.7-1ubuntu0.1",
"evidence": "/affected/0/versions"
},
{
"value": "2.10.7-1ubuntu0.2",
"evidence": "/affected/0/versions"
},
{
"value": "2.10.7-1ubuntu0.3",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "nats-server",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.10.24-1",
"evidence": "/affected/1/versions"
},
{
"value": "2.10.27-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "nats-server",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.10.27-1build1",
"evidence": "/affected/2/versions"
},
{
"value": "2.14.1-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.14.3-1",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
"value": "nats-server",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.10.27-1",
"evidence": "/affected/3/versions"
},
{
"value": "2.10.27-1build1",
"evidence": "/affected/3/versions"
},
{
"value": "2.10.27-1ubuntu0.26.04.1~esm1",
"evidence": "/affected/3/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "UBUNTU-CVE-2026-27889",
"aliases": [
"UBUNTU-CVE-2026-27889"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "nats-server",
"purl": "pkg:deb/ubuntu/nats-server?arch=source&distro=noble",
"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
"2.9.19-1build1",
"2.10.3-1",
"2.10.4-1",
"2.10.7-1",
"2.10.7-1ubuntu0.1",
"2.10.7-1ubuntu0.2",
"2.10.7-1ubuntu0.3"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27889.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "golang-github-nats-io-nats-server-dev",
"binary_version": "2.10.7-1ubuntu0.3"
},
{
"binary_name": "nats-server",
"binary_version": "2.10.7-1ubuntu0.3"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "nats-server",
"purl": "pkg:deb/ubuntu/nats-server?arch=source&distro=questing",
"ecosystem": "Ubuntu:25.10"
},
"versions": [
"2.10.24-1",
"2.10.27-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27889.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "golang-github-nats-io-nats-server-dev",
"binary_version": "2.10.27-1"
},
{
"binary_name": "nats-server",
"binary_version": "2.10.27-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "nats-server",
"purl": "pkg:deb/ubuntu/nats-server?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
"2.10.27-1build1",
"2.14.1-1",
"2.14.3-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27889.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "golang-github-nats-io-nats-server-dev",
"binary_version": "2.14.3-1"
},
{
"binary_name": "nats-server",
"binary_version": "2.14.3-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "nats-server",
"purl": "pkg:deb/ubuntu/nats-server?arch=source&distro=esm-apps%2Fresolute",
"ecosystem": "Ubuntu:Pro:26.04:LTS"
},
"versions": [
"2.10.27-1",
"2.10.27-1build1",
"2.10.27-1ubuntu0.26.04.1~esm1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27889.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "golang-github-nats-io-nats-server-dev",
"binary_version": "2.10.27-1ubuntu0.26.04.1~esm1"
},
{
"binary_name": "nats-server",
"binary_version": "2.10.27-1ubuntu0.26.04.1~esm1"
}
]
}
}
],
"modified": "2026-10-17T12:56:18.113378717Z",
"provider": "osv",
"upstream": [
"CVE-2026-27889"
],
"references": [
"https://ubuntu.com/security/CVE-2026-27889",
"https://www.cve.org/CVERecord?id=CVE-2026-27889",
"https://advisories.nats.io/CVE/secnote-2026-03.txt",
"https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6"
]
},
"related_cves": [
{
"value": "CVE-2026-27889",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 355176,
"published_at": "2026-03-25T20:16:00+00:00"
}