medium5.3
CVE-2026-33219
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system.
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/nats-io/nats-server/v2 | < 2.11.15 | 2.11.15 |
| go | github.com/nats-io/nats-server | > 0 | none recorded |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Linuxfoundation | Nats-Server | before 2.11.15 from 2.12.0 before 2.12.6 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-8r68-gvr4-jh7j
- https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j
- https://advisories.nats.io/CVE/secnote-2026-02.txt
- https://advisories.nats.io/CVE/secnote-2026-11.txt
- https://github.com/advisories/GHSA-qrvq-68c2-7grw
- https://nvd.nist.gov/vuln/detail/CVE-2026-33219
- https://access.redhat.com/errata/RHSA-2026:21769
- https://access.redhat.com/errata/RHSA-2026:22347
- https://access.redhat.com/errata/RHSA-2026:23345
- https://access.redhat.com/security/cve/CVE-2026-33219
- https://bugzilla.redhat.com/show_bug.cgi?id=2451445
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33219.json