GHSA-472h-9c5j-prrrPublished

Backstage: Inconsistent credential enforcement for overlapping proxy routes

Collected exploitation and prediction evidence

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-106456

Published

Backstage is an open framework for building developer portals. From 0.5.0 until 0.6.18, the @backstage/plugin-proxy-backend package is affected by inconsistent credential enforcement for overlapping proxy routes. 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. This issue is fixed in version 0.6.18.

Source published: 6 Oct 2026 20:10:41 UTC
Source modified: 7 Oct 2026 18:24:34 UTC
Observed here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

euvd · EUVD-2026-93989

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Oct 6, 2026, 8:10:41 PM

dateUpdated: Oct 7, 2026, 6:24:34 PM

Source published: Oct 6, 2026, 8:10:41 PM (timezone not stated)
Source modified: Oct 7, 2026, 6:24:34 PM (timezone not stated)
Observed here: 30 Oct 2026 01:52:15 UTC
Source terms: ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

nvd · CVE-2026-106456

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-863

Original publisher date fields

published: 2026-10-06T21:17:15.903

lastModified: 2026-10-27T20:51:42.720

2 source CPE criteria · context only

cpe:2.3:a:linuxfoundation:backstage\/plugin-proxy-backend:*:*:*:*:*:node.js:*:*
cpe:2.3:a:linuxfoundation:backstage:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 6 Oct 2026 21:17:15 UTC
Source modified: 27 Oct 2026 20:51:42 UTC
Observed here: 29 Oct 2026 05:48:21 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS 3.1 · [email protected] · Primary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

osv · GHSA-472h-9c5j-prrr

Published

### 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](https://github.com/backstage/backstage/releases/tag/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 published: 7 Oct 2026 20:25:13 UTC
Source modified: 7 Oct 2026 20:30:07 UTC
Observed here: 24 Oct 2026 13:17:17 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Publisher rating · MODERATE