Bug 2451449 (CVE-2026-33246)

Summary: CVE-2026-33246 nats-server: nats: github.com/nats-io/nats-server: NATS-Server: Client identity spoofing via Nats-Request-Info header manipulation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: alcohan, gparvin, jbalunas, pahickey, rhaigner
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in NATS-Server. A remote attacker, by connecting a leafnode to a NATS-Server, could propagate unchecked identity claims through the `Nats-Request-Info:` message header. This vulnerability allows for the spoofing of client identities, potentially leading to NATS clients making incorrect trust decisions based on misleading information. This could result in unauthorized information disclosure or integrity compromises within the messaging system.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2451492    
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Description OSIDB Bzimport 2026-03-25 20:02:32 UTC
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.