Backstage: Improper URL validation in catalog entity placeholder resolution

### Impact An authenticated Backstage user could craft a catalog entity with placeholder directives that reference resources outside the entity's source repository. Under certain configurations, this could allow access to data not intended to be available to the user. ### Patches Patched in `@backstage/plugin-catalog-backend` version `3.9.1` ### Workarounds If you're not able to update immediately: - Limit the scope of integration credentials (e.g., GitHub tokens) to only the repositories that Backstage needs to access.

Source published

7 Oct 2026 17:59:24 UTC

Source modified

7 Oct 2026 18:15:10 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

Publisher rating · HIGH