# CVE-2026-106495: Backstage backend-defaults improper access control in action invocation

Source: https://junglewise.ai/threats/cve-2026-106495-backstage-improper-access-control-in-backend-action-invocation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-12. Updated: 2026-10-15  
License: CC BY 4.0 with a link back

CVE-2026-106495 · Severity: medium · CVSS 4.3 · Published 2026-10-12

Backstage is an open platform for building internal developer portals. An authenticated user could bypass operator-configured action restrictions to invoke excluded actions, allowing unauthorized workflow automation. Existing downstream permissions remain enforced, limiting the exposure.

Technologies: [Backstage Backend-Defaults](https://junglewise.ai/threats/technologies/backend-defaults), [@backstage/backend-defaults (npm)](https://junglewise.ai/threats/technologies/backstage-backend-defaults). Vendors: [Backstage](https://junglewise.ai/threats/vendors/backstage), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-106495 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-106495 being exploited in the wild.

**How severe is CVE-2026-106495?** Medium severity, with a CVSS score of 4.3, published 12 October 2026.

**Which products and versions are affected?** Backstage Backend-Defaults < 0.17.8; @backstage/backend-defaults (npm) < 0.17.8, SEMVER:introduced=0,fixed=0.17.8.

**Is there a fix for CVE-2026-106495?** Yes. @backstage/backend-defaults (npm): upgrade to 0.17.8 or later. Until then: Limit access to action invocation endpoints to trusted service callers until upgrading. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-106495 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-106495?** Check whether you run Backstage Backend-Defaults or @backstage/backend-defaults (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @backstage/backend-defaults (npm): upgrade to 0.17.8 or later

  ```sh
  npm install @backstage/backend-defaults@0.17.8
  ```


Limit access to action invocation endpoints to trusted service callers until upgrading.

## Technical details

An improper access control vulnerability (CWE-284) in the backend action invocation logic allows authenticated users to bypass operator-configured action filtering. The vulnerability is exploitable over the network by authenticated users without user interaction. An attacker gains the ability to invoke administrative actions that were intended to be excluded, though downstream authorization checks still apply.

## Affected products

- Backstage backend-defaults < 0.17.8

## Identifiers

- CVE-2026-106495
- GHSA-3xr5-8w6c-p5gw

## Timeline

- 2026-08-28: disclosed
- 2026-10-15: advisory
- 2026-10-15: patched

## References

- [https://github.com/backstage/backstage/security/advisories/GHSA-3xr5-8w6c-p5gw](https://github.com/backstage/backstage/security/advisories/GHSA-3xr5-8w6c-p5gw)

## Related threats

- [Backstage backend-defaults path traversal in cloud storage URL readers](https://junglewise.ai/threats/cve-2026-106494-backstage-is-an-open-framework-for-building-developer-portals)
- [Backstage: Cloud storage catalog locations may cross configured storage boundaries](https://junglewise.ai/threats/cve-2026-106493-backstage-is-an-open-framework-for-building-developer-portals)
- [Backstage backend-defaults service credential delegation bypass](https://junglewise.ai/threats/cve-2026-106492-backstage-is-an-open-framework-for-building-developer-portals)
- [Backstage Scaffolder symlink path traversal in multiple actions](https://junglewise.ai/threats/cve-2026-24046-backstage-scaffolder-symlink-path-traversal-in-multiple-actions)
- [Backstage SSRF in FetchUrlReader via HTTP redirects](https://junglewise.ai/threats/cve-2026-24048-backstage-ssrf-in-fetchurlreader-via-http-redirects)