Description
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 malicious client which can connect to the WebSockets port can cause unbounded memory use in the nats-server before authentication; this requires sending a corresponding amount of data. This is a milder variant of CVE-2026-27571. That earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable websockets if not required for project deployment.
Details
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Affected Packages
| Software | From version | Fixed in |
|---|---|---|
| github.com/nats-io/nats-server | โ | โ |
| github.com/nats-io/nats-server/v2 | โ | โ |
| nats | โ | โ |
| nats-server | 2.12.0 | 2.12.6 |
References
Similar Threats
- High CVE-2026-27889
- High CVE-2026-29785
- Medium CVE-2026-33215
- High CVE-2026-33216
- High CVE-2026-33217
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