Auth bypass in @Backstage Plugin-Auth-Backend-Module-Cloudflare-Access-Provider

CVE-2026-106457

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.

Vulnerability class: Broken Authentication

Published .

CVSS v3 metric

CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-106457?
CVE-2026-106457 is a medium-severity vulnerability in @Backstage Plugin-Auth-Backend-Module-Cloudflare-Access-Provider, classified under Improper Authentication. CVSS score: 6.8/10. Published 2026-10-06.
How severe is CVE-2026-106457?
Medium severity. CVSS v3 base score is 6.8 out of 10.