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Fencer Intel
medium 6.8

CVE-2026-106457 json

Backstage: Insufficient audience validation in the Cloudflare Access auth provider

published last mo. modified 13d ago also GHSA-q333-f498-w2x7 , EUVD-2026-93990

cvss
6.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits
0
none known

Summary

Backstage is an open framework for building developer portals. From 0.1.0 until 0.5.0, the @backstage/plugin-auth-backend-module-cloudflare-access-provider package is affected by insufficient audience validation in the cloudflare access auth provider. 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. This issue is fixed in version 0.5.0.

Patch / fix

  • npm @backstage/plugin-auth-backend-module-cloudflare-access-provider 0.5.0
  • linuxfoundation backstage/plugin-auth-backend-module-cloudflare-access-provider 0.5.0
  • linuxfoundation backstage 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-2026-106457 updated cvss 6.8

plugin-auth-backend-module-cloudflare-access-provider: Backstage: Unauthorized access via missing token audience validation

  • Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Self-service automation portal 2 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
total
Assessed
last mo.

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
GitHub 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
npm @backstage/plugin-auth-backend-module-cloudflare-access-provider
>=0.1.0, <0.5.0
0.5.0

Affected products

  • backstage backstage
  • @backstage plugin-auth-backend-module-cloudflare-access-provider

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.