Resource exhaustion in Linuxfoundation Nats-Server
CVE-2026-33219
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.
EPSS: 0.005 (41.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
Affected products
- Linuxfoundation Nats-server
- Nats-io Nats-server — versions < 2.11.15, >= 2.12.0-RC.1, < 2.12.6
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Mitigation, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Mitigation, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Mitigation, Vendor Advisory)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-33219?
- CVE-2026-33219 is a medium-severity vulnerability in Linuxfoundation Nats-Server, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.3/10. Published 2026-03-25.
- How severe is CVE-2026-33219?
- Medium severity. CVSS v3 base score is 5.3 out of 10.