All vulnerabilities
CVE-2026-106456GHSA-472h-9c5j-prrr

@backstage/plugin-proxy-backend: Backstage: Inconsistent credential enforcement for overlapping proxy routes

backstage @backstage/plugin-proxy-backendnpmLibraries & packages
Open in ThreatlineRecord JSON
CVSS
4.8Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.24%Chance of exploitation activity in the next 30 days, higher than 13% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in0.6.18Fixed versionGitHub
Published6 Oct 2026Updated 7 Oct 2026CVE List

What fixes it

  • 0.6.18@backstage/plugin-proxy-backend, npmGitHubnpm install @backstage/plugin-proxy-backend@0.6.18

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

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.

Text from GitHub Advisory Database

Affected versions 4

  • @backstage/plugin-proxy-backend, npm>= 0.5.0, < 0.6.18GitHub
  • backstageaffected: >= 1.28.0, < 1.55.0CVE List
  • plugin-proxy-backendaffected: >= 0.5.0, < 0.6.18CVE List
  • @backstage/plugin-proxy-backend, npmfrom 0.5.0, fixed in 0.6.18OSV

References 5