CVE-2026-33219
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk41th percentile - higher than 41% of all known CVEs
Summary
A vulnerability in NATS-Server before versions 2.11.15 and 2.12.6 allows a malicious client to cause unbounded memory usage before authentication via WebSockets connections. The attack requires sending a corresponding amount of data, making it a milder variant of CVE-2026-27571.
Risk Assessment
The organization risks memory exhaustion on the server, potentially leading to denial of service (DoS) and disruption of NATS-based communication systems.
Recommendation
Immediately update NATS-Server to version 2.11.15 or 2.12.6. As a workaround, disable WebSockets if not required for the project deployment.
Original NVD description (English source)
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.