CVE-2026-106457: @backstage Plugin-Auth-Backend-Module-Cloudflare-Access-Provider

Medium severity, CVSS 6.8. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• @backstage Plugin-Auth-Backend-Module-Cloudflare-Access-Provider: from 0.1.0, before 0.5.0 (fixed in 0.5.0)
• Backstage Backstage: from 1.26.0, before 1.55.0 (fixed in 1.55.0)

Published 2026-10-06. Last modified 2026-10-07.