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Fencer Intel
medium 5.9

CVE-2026-32235 json

@backstage/plugin-auth-backend: OAuth redirect URI allowlist bypass

published 7mo ago modified 4mo ago also GHSA-wqvh-63mv-9w92 , EUVD-2026-11671

cvss
5.9
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 6%
public exploits
0
none known

Summary

Backstage is an open framework for building developer portals. Prior to 0.27.1, the experimental OIDC provider in @backstage/plugin-auth-backend is vulnerable to a redirect URI allowlist bypass. Instances that have enabled experimental Dynamic Client Registration or Client ID Metadata Documents and configured allowedRedirectUriPatterns are affected. A specially crafted redirect URI can pass the allowlist validation while resolving to an attacker-controlled host. If a victim approves the resulting OAuth consent request, their authorization code is sent to the attacker, who can exchange it for a valid access token. This requires victim interaction and that one of the experimental features is explicitly enabled, which is not the default. This vulnerability is fixed in 0.27.1.

Patch / fix

  • npm @backstage/plugin-auth-backend 0.27.1

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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-2026-32235 updated cvss 5.9

@backstage/plugin-auth-backend: @backstage/plugin-auth-backend: OAuth redirect URI allowlist bypass

  • Red Hat Self-service automation portal 2 ansible-automation-platform/automation-portal
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Developer Hub 1.10 rhdh/rhdh-hub-rhel9 1780930740
    fixed: vendor fix RHSA-2026:24841
  • Red Hat Developer Hub 1.10 rhdh/rhdh-rhel9-operator 1779927546, rhdh/rhdh-operator-bundle 1780961472
    not affected: vulnerable code not present

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
7mo ago

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N
NVD 3.1 4.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N
GitHub 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm @backstage/plugin-auth-backend
<0.27.1
0.27.1

Affected products

  • @backstage plugin-auth-backend

Classification

Weakness
  • CWE-601 URL Redirection to Untrusted Site
  • CWE-20 Improper Input Validation

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.