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Fencer Intel
medium 4.8

CVE-2026-106456 json

Backstage: Inconsistent credential enforcement for overlapping proxy routes

published last mo. modified 13d ago also EUVD-2026-93989 , GHSA-472h-9c5j-prrr

cvss
4.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 15%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm @backstage/plugin-proxy-backend 0.6.18
  • linuxfoundation backstage/plugin-proxy-backend 0.6.18
  • linuxfoundation backstage 0.6.18, 1.55.0
  • linuxfoundation @backstage/techdocs-common 1.55.0
  • linuxfoundation backstage_core-components 1.55.0
  • linuxfoundation backstage_catalog-model 1.55.0
  • linuxfoundation backstage_plugin-catalog-backend 1.55.0
  • linuxfoundation @backstage/plugin-techdocs 1.55.0
  • linuxfoundation auth_backend 1.55.0

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-106456 updated cvss 4.8

plugin-proxy-backend: plugin-proxy-backend: Authentication bypass via overlapping proxy routes

  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Self-service automation portal 2 ansible-automation-platform/automation-portal, ansible-automation-platform/bootc-automation-portal-rhel9
    affected: no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
last mo.

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
GitHub 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm @backstage/plugin-proxy-backend
>=0.5.0, <0.6.18
0.6.18

Affected products

  • backstage backstage
  • @backstage plugin-proxy-backend

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.