CVE-2026-73563

Name of the Vulnerable Software and Affected Versions Backstage versions prior to 0.29.2

Description Experimental dynamic client registration and client ID metadata document features in the @backstage/plugin-auth-backend use full-string matcher.isMatch glob matching for the auth.experimentalDynamicClientRegistration.allowedRedirectUriPatterns and the auth.experimentalClientIdMetadataDocuments allowedClientIdPatterns and allowedRedirectUriPatterns options. A hostname wildcard can match across URL component boundaries, which allows an attacker-controlled redirect URI with a trusted hostname suffix in its path to bypass the allowlist and receive an OAuth authorization code. Additionally, patterns lacking an explicit protocol can match unintended protocols, and redirect URIs containing embedded credentials are accepted after user information is stripped for matching. These features are disabled by default; only deployments that enable them and configure custom wildcard-hostname or protocol-less patterns are affected.

Recommendations Update to version 0.29.2 or later.