NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
Description
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.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
github.com/nats-io/nats-server/v2Go | >= 2.2.0, < 2.11.14 | 2.11.14 |
github.com/nats-io/nats-server/v2Go | >= 2.12.0, < 2.12.5 | 2.12.5 |
github.com/nats-io/nats-serverGo | >= 0 | — |
Affected products
1- Range: >= 2.2.0, < 2.11.14
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
4- github.com/advisories/GHSA-pq2q-rcw4-3hr6ghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-27889ghsaADVISORY
- advisories.nats.io/CVE/secnote-2026-03.txtghsax_refsource_MISCWEB
- github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6ghsax_refsource_CONFIRMWEB
News mentions
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