NATS is vulnerable to pre-auth DoS through WebSockets client service
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 2.11.15, 2.12.6
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
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.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- nats-io nats-server
fixed in 2.11.15; From 2.12.0-RC.1 · fixed in 2.12.6
- github.com/nats-io/nats-serverGo
All versions
- github.com/nats-io/nats-server/v2Go
fixed in 2.11.15; From 2.12.0-RC.1 · fixed in 2.12.6
- github.com/nats-io/nats-server/v2Go
fixed in 2.11.15
- github.com/nats-io/nats-server/v2Go
From 2.12.0-RC.1 · fixed in 2.12.6