NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
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.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-27889US | — | — | ||
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… | ||||
references
External citations — patches, advisories, analysis.
- https://access.redhat.com/errata/RHSA-2026:21769WEB
- https://access.redhat.com/errata/RHSA-2026:22347WEB
- https://access.redhat.com/errata/RHSA-2026:23345WEB
- https://access.redhat.com/security/cve/CVE-2026-27889WEB
- https://advisories.nats.io/CVE/secnote-2026-03.txtADVISORY
- https://bugzilla.redhat.com/show_bug.cgi?id=2451447WEB
- https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6ADVISORY
- https://nvd.nist.gov/vuln/detail/CVE-2026-27889WEB
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