Bug 2539759 (CVE-2026-67404)

Summary: CVE-2026-67404 rabbitmq-server: rabbitmq-server: OAuth2 silent verify_none fallback for JWKS fetch
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
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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Doc Text:
A flaw was found in rabbitmq-server. When the OAuth2 plugin fetches JWKS and no CA bundle is available, TLS verification silently falls back to verify_none. A man-in-the-middle attacker can forge the JWKS response, causing the broker to accept arbitrary JWTs.
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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: 2547951    
Bug Blocks:    

Description OSIDB Bzimport 2026-09-23 20:32:31 UTC
RabbitMQ is a messaging and streaming broker. Prior to versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0, When no CA bundle is available, ssl_options/1 falls back to [{verify, verify_none}] with no warning. An attacker in a man-in-the-middle position can forge the JWKS response, which leads the broker to accept arbitrary JWTs. Preconditions include The OAuth2 plugin must be in use with no cacertfile configured and the OS CA bundle empty or unreadable (for example, in a minimal container), and the attacker must hold a network man-in-the-middle position.. This issue is fixed in versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0.

Comment 1 Yadnyawalk Tale 2026-10-08 12:58:01 UTC
CVSS Justifications
====================
AV:N -- JWKS fetched over the network; MITM forges it
AC:H -- Requires OAuth2 + missing CA trust + MITM
PR:N -- No broker privileges required
UI:N -- No user interaction
S:U -- Impact stays on the broker
C/I/A:H -- Arbitrary JWTs enable full authentication bypass