CVE-2026-32235@backstage/plugin-auth-backend: OAuth redirect URI allowlist bypass

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.

CVSS

5.9 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N

Weakness (CWE)

CWE-601

Known exploited

Not in CISA's KEV catalog

EPSS (exploitation in the next 30 days)

Not loaded for this CVE

Assigned by

GitHub_M

NVD analysis

Undergoing Analysis

Record last updated

Mar 12, 2026

First seen by InfoSec Signals

Oct 9, 2026

The CVE record on cve.org · NVD's entry

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