Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-73563

CVE-2026-73563MEDIUM

Backstage: Unauthenticated OAuth account takeover via `redirect_uri` allowlist bypass in `@backstage/plugin-auth-backend`

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   R  C  L  L  N    6.1   .0017    6.1     —

AFFECTED
  Product    Versions    Fixed
  backstage  < 0.29.2 –  —

TIMELINE
  Aug 12  Reserved by GitHub_M
  Aug 13  Published (CNA: GitHub_M)
  Oct 15  RESCORED — CVE-2026-73563 (backstage). CVSS 4.7 → 6.1 (NVD).

CWE-601 · CNA: GitHub_M · CVSS v3.1 · 1 reference · NVD status: Analyzed

Description

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
August 12, 2026	Reserved	Reserved by GitHub_M
August 13, 2026	Published	Published (CNA: GitHub_M)
October 15, 2026	RESCORED	RESCORED — CVE-2026-73563 (backstage). CVSS 4.7 → 6.1 (NVD).

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
backstage	backstage	—	< 0.29.2	—

Weaknesses

CWE-601

References (1)

https://github.com/backstage/backstage/security/advisories/GHSA-38hq-7x33-php4 [Mitigation, Vendor Advisory]

Authoritative record: CVE-2026-73563 at cve.org

Vendors: backstage

Weaknesses: CWE-601

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-73563 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.