Backstage has a Possible SSRF when reading from allowed URL's in `backend.reading.allow`

Summary

Backstage is an open framework for building developer portals, and @backstage/backend-defaults provides the default implementations and setup for a standard Backstage backend app. Prior to versions 0.12.2, 0.13.2, 0.14.1, and 0.15.0, the `FetchUrlReader` component, used by the catalog and other plugins to fetch content from URLs, followed HTTP redirects automatically. This allowed an attacker who controls a host listed in `backend.reading.allow` to redirect requests to internal or sensitive URLs that are not on the allowlist, bypassing the URL allowlist security control. This is a Server-Side Request Forgery (SSRF) vulnerability that could allow access to internal resources, but it does not allow attackers to include additional request headers. This vulnerability is fixed in `@backstage/backend-defaults` version 0.12.2, 0.13.2, 0.14.1, and 0.15.0. Users should upgrade to this version or later. Some workarounds are available. Restrict `backend.reading.allow` to only trusted hosts that you control and that do not issue redirects, ensure allowed hosts do not have open redirect vulnerabilities, and/or use network-level controls to block access from Backstage to sensitive internal endpoints.

Timeline

1. Jan 21, 2026, 10:51 PM UTCCVE published
2. Jan 22, 2026, 3:09 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Jan 22, 2026, 4:48 PM UTCRecord last updated

Affected versions

• backstage backstage

  fixed in 0.12.2; From 0.13.0 · fixed in 0.13.2; From 0.14.0 · fixed in 0.14.1

• @backstage/backend-defaultsnpm

  fixed in 0.12.2

• @backstage/backend-defaultsnpm

  From 0.13.0 · fixed in 0.13.2

• @backstage/backend-defaultsnpm

  From 0.14.0 · fixed in 0.14.1

References 2