Authorization Flaw in @backstage/plugin-proxy-backend (CVE-2026-106456)
Summary
Vulnerability in @backstage/plugin-proxy-backend (CVE-2026-106456). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 0.6.18 or later.
Original description
The description as published by the source.
Impact
An operator can configure overlapping proxy paths with different credential requirements. When a parent path permits unauthenticated access and a nested path requires credentials, the parent exemption can also cover requests handled by the nested proxy. An unauthenticated caller may therefore reach the nested upstream through Backstage, including with static upstream credentials configured for that proxy.
Exploitation requires this specific overlapping route configuration. The resulting confidentiality and integrity impact depends on the capabilities exposed by the nested upstream.
Patches
Upgrade @backstage/plugin-proxy-backend to version 0.6.18 or later. The fixed package is available in Backstage v1.55.0.
Workarounds
- Avoid nesting a credential-protected proxy path below a path configured with
dangerously-allow-unauthenticated. - Apply the same credential requirement to overlapping proxy paths.
- Restrict direct network access to the Backstage backend until the patched package is deployed.
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-2026-106456 has been found in @backstage/plugin-proxy-backend.
Risk of unauthorized operations or information disclosure. CVSS score: 4.8/10.
What to do: upgrade @backstage/plugin-proxy-backend to 0.6.18 or later.
If unsure, ask your IT team or search "@backstage/plugin-proxy-backend CVE-2026-106456" on the vendor's site.
CVE-2026-106456 (@backstage/plugin-proxy-backend) — CWE-863 / CVSS v3 4.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 0.6.18 — 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.
Incorrect authorization (CWE-863) exists in @backstage/plugin-proxy-backend.
Check the vendor advisory for the affected versions of @backstage/plugin-proxy-backend.
Severity: Medium (CVSS 4.8/10). Risk of unauthorized operations or information disclosure.
Update to 0.6.18.
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-proxy-backend' . 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-proxy-backend' . | 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-proxy-backend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-proxy-backend to 0.6.18ステージング環境で 0.6.18 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