Medium [CVE-2026-73563] @backstage/plugin-auth-backend: Backstage: Unauthenticated OAuth account takeover via `redirect_uri` allowlist bypass
This medium-severity Red Hat Linux advisory covers CVE-2026-73563 affecting Red Hat Ansible Automation Platform 2.1, Red Hat Ansible Automation Platform 2.2.
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Summary
Backstage is an open framework for building developer portals.
Prior to 0.29.2, the experimental dynamic client registration and client ID metadata document features in the @backstage/plugin-auth-backend use full-string matcher.isMatch glob matching for auth.experimentalDynamicClientRegistration.allowedRedirectUriPatterns and the auth.experimentalClientIdMetadataDocuments allowedClientIdPatterns and allowedRedirectUriPatterns options.
A hostname wildcard can match across URL component boundaries, allowing an attacker-controlled redirect URI with a trusted hostname suffix in its path to pass the allowlist and receive an OAuth authorization code after a victim completes the flow.
Patterns without an explicit protocol can match unintended protocols, and redirect URIs containing embedded credentials are accepted after user information is stripped for matching. The features are experimental and disabled by default; only deployments that enable them and configure custom wildcard-hostname or protocol-less patterns are affected.
This issue is first fixed in prerelease version 0.29.2. This vulnerability allows an unauthenticated remote attacker to bypass the `redirect_uri` allowlist in the experimental dynamic client registration feature.
Affected products named by the advisory: Red Hat Ansible Automation Platform 2.1; Red Hat Ansible Automation Platform 2.2.
- < 0.29.2
Official advisory · high-confidence parse· fetched 24 days ago·verify at source
- 0.29.2
- ansible-automation-platform/automation-portal:1788775748
- ansible-automation-platform/automation-portal:1788783591
- RHSA-2026:65118
- RHSA-2026:65155
Official advisory · high-confidence parse· fetched 24 days ago·verify at source
Mitigation checklist
- Do not enable the experimental dynamic client registration or client ID metadata document features. If these features are currently enabled, review and restrict the allowedRedirectUriPatterns and allowedClientIdPatterns configurations to use fully qualified hostnames with explicit protocols rather than wildcard or protocol-less patterns.
Official advisory · high-confidence parse· fetched 24 days ago·verify at source
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