Bug 2541515 (CVE-2026-66071)

Summary: CVE-2026-66071 rabbitmq-server: rabbitmq-server: Denial of service via atom exhaustion in OAuth2 JWT scope parsing
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: eglynn, jjoyce, jpretori, jschluet, lhh, mburns, mgarciac
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in rabbitmq-server where its OAuth2 authentication backend improperly converts token scope values into Erlang runtime atoms. In deployments where an Identity Provider (IdP) allows users to influence scope contents within their signed JSON Web Tokens (JWTs), an authenticated attacker can supply unique scope tags across multiple authentications. This gradually depletes the broker's non-garbage-collected atom table, ultimately crashing the broker and causing a denial of service (DoS).
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Description OSIDB Bzimport 2026-09-25 16:45:58 UTC 
RabbitMQ is a messaging and streaming broker. From 3.13.0 until 3.13.15 and 4.0.22 and 4.1.11 and 4.2.6 and 4.3.1, Atom exhaustion: OAuth2 JWT tag: scope values. extractscopes/1 parses scopes of the form .tag: and calls rabbitdatacoercion:toatom() to convert to a tag atom. The token signature is verified first, so the attacker cannot forge scopes , but in IdP configurations where scope content is user-influenced, each login with a novel tag value leaks one In deployments where users can influence the scopes included in their IdP-issued JWT rabbitmqauthbackendoauth2 enabled IdP permits attacker-influenced scope values in signed tokens. This issue is fixed in versions 3.13.15 and 4.0.22 and 4.1.11 and 4.2.6 and 4.3.1.