CVE-2026-73563
MediumCVSS 4.7Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
Backstage before version 0.29.2 has a vulnerability in the experimental dynamic client registration and client ID metadata document features in @backstage/plugin-auth-backend. Full-string glob matching can be bypassed, 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. These features are experimental and disabled by default.
Risk Assessment
Risk of account takeover or unauthorized access in environments that have enabled these experimental features.
Recommendation
Upgrade Backstage to version 0.29.2 or later if using these features; otherwise ensure they are disabled.
Original NVD description (English source)
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.