Medium, CVSS 6.8npmAmendedPublished
Backstage: Insufficient audience validation in the Cloudflare Access auth provider
CVE-2026-106457 · GHSA-q333-f498-w2x7
- Affected
- npm @backstage/plugin-auth-backend-module-cloudflare-access-provider >= 0.1.0, < 0.5.0
- Fixed in
- 0.5.0· Vendor fix available
- Issue
- Impact 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. The reported reproduction exercises the provider directly and does not demonstrate bypass through the ordinary Cloudflare-protected Backstage URL. Relevant deployment topologies include direct origin access, alternate routes around the intended Access application, or another proxy forwarding the assertion unchanged. A successful sign-in also depends on the deployment's sign-in resolver mapping the presented identity to a Backstage user. The resulting…
Recommended action: Upgrade to 0.5.0 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.