Bug 2547145 (CVE-2026-106457)

Summary:	CVE-2026-106457 plugin-auth-backend-module-cloudflare-access-provider: Backstage: Unauthorized access via missing token audience validation
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	abarbaro, alizardo, dschmidt, ikhan, jchui, jhe, jlanda, kshier, ktsao, nboldt, oaljalju, psrna, rbobbitt, simaishi, stcannon, yguenane
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in the Backstage Cloudflare Access authentication provider module. This vulnerability allows an attacker to gain unauthorized access to the Backstage application. The provider verifies a token's signature and team issuer but fails to confirm that the token was issued for the Backstage application. Consequently, a remote attacker holding a valid token for another application within the same Cloudflare Zero Trust team can authenticate to Backstage if the request reaches the authentication endpoint without upstream audience enforcement.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-06 20:22:44 UTC

Backstage is an open framework for building developer portals. From 0.1.0 until 0.5.0, the @backstage/plugin-auth-backend-module-cloudflare-access-provider package is affected by insufficient audience validation in the cloudflare access auth provider. The Cloudflare Access auth provider verifies a token's signature and team issuer, but affected versions do not verify that the token was issued for the Backstage application. A user holding a valid token for another Access application in the same Cloudflare Zero Trust team may therefore be able to authenticate to Backstage if that token reaches the auth endpoint without the Backstage application's audience already being enforced upstream. Cloudflare Access normally evaluates the protected application before forwarding requests. This issue is fixed in version 0.5.0.