CVE-2026-33246— NATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers
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之前版本存在安全漏洞，该漏洞源于Nats-Request-Info标头身份声明未经验证传播，可能导致客户端被欺骗。
Possible ATT&CK Techniques 1 AI
T1134 · Access Token Manipulation
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I. Basic Information for CVE-2026-33246
Vulnerability Information
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Vulnerability Title
NATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers
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. The nats-server offers a `Nats-Request-Info:` message header, providing information about a request. This is supposed to provide enough information to allow for account/user identification, such that NATS clients could make their own decisions on how to trust a message, provided that they trust the nats-server as a broker. A leafnode connecting to a nats-server is not fully trusted unless the system account is bridged too. Thus identity claims should not have propagated unchecked. Prior to versions 2.11.15 and 2.12.6, NATS clients relying upon the Nats-Request-Info: header could be spoofed. This does not directly affect the nats-server itself, but the CVSS Confidentiality and Integrity scores are based upon what a hypothetical client might choose to do with this NATS header. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5
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Nats-Request-Info标头身份声明未经验证传播，可能导致客户端被欺骗。
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-2026-33246
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Advisories for CVE-2026-33246 (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-2026-33218 | 7.5 HIGH | NATS has pre-auth server panic via leafnode handling |
| 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-2026-33223 | 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
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CVE-2026-58208
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CVE-2026-58209
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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-287
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CVE-2026-110864
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Better Auth @better-auth/sso before 1.7.3 Authentication Byp -
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V. Comments for CVE-2026-33246
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