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CVE-2026-33219— NATS is vulnerable to pre-auth DoS through WebSockets client service

CVSS 5.3 · Medium EPSS 0.11% · P29
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I. Basic Information for CVE-2026-33219

Vulnerability Information
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Vulnerability Title
NATS is vulnerable to pre-auth DoS through WebSockets client service
Source: NVD (National Vulnerability Database)
Vulnerability 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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: NVD (National Vulnerability Database)
Vulnerability Type
不加限制或调节的资源分配
Source: NVD (National Vulnerability Database)
Vulnerability Title
Nats-Server 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Nats-Server是Nats开源的一个用于 Nats.io、云和边缘本机消息传递系统的高性能服务器。 Nats-Server 2.11.15之前版本和2.12.6之前版本存在安全漏洞，该漏洞源于恶意客户端可导致无限制内存使用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
nats-ionats-server < 2.11.15 -

II. Public POCs for CVE-2026-33219

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III. Intelligence Information for CVE-2026-33219

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Same Patch Batch · nats-io · 2026-03-25 · 12 CVEs total

CVE-2026-332168.6 HIGHNATS has MQTT plaintext password disclosure
CVE-2026-278897.5 HIGHNATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
CVE-2026-297857.5 HIGHNATS Server panic via malicious compression on leafnode port
CVE-2026-332187.5 HIGHNATS has pre-auth server panic via leafnode handling
CVE-2026-332477.4 HIGHNATS credentials are exposed in monitoring port via command-line argv
CVE-2026-332177.1 HIGHNATS allows MQTT clients to bypass ACL checks
CVE-2026-332466.4 MEDIUMNATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers
CVE-2026-332236.4 MEDIUMNATS Server: Incomplete Stripping of Nats-Request-Info Header Allows Identity Spoofing
CVE-2026-332224.9 MEDIUMNATS JetStream has an authorization bypass through its Management API
CVE-2026-332494.3 MEDIUMNATS: Message tracing can be redirected to arbitrary subject
CVE-2026-332484.2 MEDIUMNATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching

IV. Related Vulnerabilities

Same product: nats-server
Same vendor: nats-io
Same weakness: CWE-770

V. Comments for CVE-2026-33219

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