CVE-2026-33218— NATS has pre-auth server panic via leafnode handling
Quick assessment
Affected
nats-io nats-server
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
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之前版本存在输入验证错误漏洞，该漏洞源于客户端可发送特定畸形消息，可能导致服务器崩溃。
Possible ATT&CK Techniques 1 AI
T1496 · Resource HijackingAffected Version Matrix 2
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| nats-io | nats-server | < < 2.11.15 |
affected |
>= 2.12.0-RC.1, < 2.12.6 |
affected |
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I. Basic Information for CVE-2026-33218
Vulnerability Information
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Vulnerability Title
NATS has pre-auth server panic via leafnode handling
Source: CVE Program / CVE List V5
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 client which can connect to the leafnode port can crash the nats-server with a certain malformed message pre-authentication. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable leafnode support if not needed or restrict network connections to the leafnode port, if plausible without compromising the service offered.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Nats-Server 输入验证错误漏洞
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之前版本存在输入验证错误漏洞，该漏洞源于客户端可发送特定畸形消息，可能导致服务器崩溃。
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
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| nats-io | nats-server | < < 2.11.15 | - |
|
II. Public POCs for CVE-2026-33218
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Advisories for CVE-2026-33218 (1)
Same Patch Batch · nats-io · 2026-03-25 · 12 CVEs total
| CVE-2026-33216 | 8.6 HIGH | NATS has MQTT plaintext password disclosure |
| CVE-2026-27889 | 7.5 HIGH | NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead |
| CVE-2026-29785 | 7.5 HIGH | NATS Server panic via malicious compression on leafnode port |
| CVE-2026-33247 | 7.4 HIGH | NATS credentials are exposed in monitoring port via command-line argv |
| CVE-2026-33217 | 7.1 HIGH | NATS allows MQTT clients to bypass ACL checks |
| CVE-2026-33246 | 6.4 MEDIUM | NATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers |
| CVE-2026-33223 | 6.4 MEDIUM | NATS Server: Incomplete Stripping of Nats-Request-Info Header Allows Identity Spoofing |
| CVE-2026-33219 | 5.3 MEDIUM | NATS is vulnerable to pre-auth DoS through WebSockets client service |
| CVE-2026-33222 | 4.9 MEDIUM | NATS JetStream has an authorization bypass through its Management API |
| CVE-2026-33249 | 4.3 MEDIUM | NATS: Message tracing can be redirected to arbitrary subject |
| CVE-2026-33248 | 4.2 MEDIUM | NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching |
IV. Related Vulnerabilities
Same product: nats-server
-
CVE-2026-58208
NATS Server: MQTT-over-WebSocket Path Can Crash WebSocket-On -
CVE-2026-58211
NATS Server: `no_auth_user` pre-CONNECT fast path bypasses u -
CVE-2026-58207
NATS Server: Remote crash via integer overflow in Connz pagi -
CVE-2026-58210
NATS Server: MQTT partial CONNECT packets can exhaust pre-au -
CVE-2026-58209
NATS Server: MQTT retained and QoS replay bypass subscribe d
Same vendor: nats-io
-
CVE-2026-58208
NATS Server: MQTT-over-WebSocket Path Can Crash WebSocket-On -
CVE-2026-58211
NATS Server: `no_auth_user` pre-CONNECT fast path bypasses u -
CVE-2026-58207
NATS Server: Remote crash via integer overflow in Connz pagi -
CVE-2026-58210
NATS Server: MQTT partial CONNECT packets can exhaust pre-au -
CVE-2026-58209
NATS Server: MQTT retained and QoS replay bypass subscribe d
Same weakness: CWE-20
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V. Comments for CVE-2026-33218
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