@backstage/plugin-auth-backend: OAuth redirect URI allowlist bypass
Impact
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.
Patches
Upgrade to @backstage/plugin-auth-backend version 0.27.1 or later.
Workarounds
Disable experimental Dynamic Client Registration and Client ID Metadata Documents features if they are not required.
References
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @backstage/plugin-auth-backend | < 0.27.1 | 0.27.1 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N- Weakness (CWE)
CWE-20, CWE-601- Platform
- npm
- Package
@backstage/plugin-auth-backend- Disclosed
- 12.03.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-wqvh-63mv-9w92 - CC BY 4.0
Vulnerability history: @backstage/plugin-auth-backend
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 4
- First → latest
- 12.2021 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 2
- Low 1
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 3
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@backstage/plugin-auth-backend: OAuth redirect URI allowlist bypass this entry
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