Authentication Bypass in @backstage/plugin-auth-backend-module-cloudflare-access-provider (CVE-2026-106457)
Summary
Authentication bypass in @backstage/plugin-auth-backend-module-cloudflare-access-provider (CVE-2026-106457). Confidential information can be exposed externally. Exploitable via auth.providers.cfaccess.audience. Mitigation: upgrade to 0.5.0 or later.
Original description
The description as published by the source.
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 impact depends on the permissions assigned to that identity.
Patches
Upgrade @backstage/plugin-auth-backend-module-cloudflare-access-provider to version 0.5.0 or later. The fixed package is available in Backstage v1.55.0.
This is a breaking configuration change. Before upgrading, set auth.providers.cfaccess.audience to the Audience (AUD) tag for the Backstage application in Cloudflare Zero Trust:
auth:
prov…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-106457 has been found in @backstage/plugin-auth-backend-module-cloudflare-access-provider.
Attackers can target a specific entry point like auth.providers.cfaccess.audience over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 6.8/10.
What to do: upgrade @backstage/plugin-auth-backend-module-cloudflare-access-provider to 0.5.0 or later.
If unsure, ask your IT team or search "@backstage/plugin-auth-backend-module-cloudflare-access-provider CVE-2026-106457" on the vendor's site.
CVE-2026-106457 (@backstage/plugin-auth-backend-module-cloudflare-access-provider) — CWE-287 / CVSS v3 6.8
Attack vector: remote (network-reachable) / no user interaction
Attack surface: auth.providers.cfaccess.audience
Patched: 0.5.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Authentication bypass (CWE-287) exists in @backstage/plugin-auth-backend-module-cloudflare-access-provider. Attackers reach the vulnerable code path via auth.providers.cfaccess.audience.
Check the vendor advisory for the affected versions of @backstage/plugin-auth-backend-module-cloudflare-access-provider. Attack surface: auth.providers.cfaccess.audience.
Severity: Medium (CVSS 6.8/10). Confidential information can be exposed externally.
Update to 0.5.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r '@backstage/plugin-auth-backend-module-cloudflare-access-provider' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r '@backstage/plugin-auth-backend-module-cloudflare-access-provider' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
@backstage/plugin-auth-backend-module-cloudflare-access-providerを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade @backstage/plugin-auth-backend-module-cloudflare-access-provider to 0.5.0ステージング環境で 0.5.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com