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Backstage: Improper access control in backend action invocation

Moderate severity GitHub Reviewed Published Aug 28, 2026 in backstage/backstage • Updated Oct 15, 2026

Package

npm @backstage/backend-defaults (npm)

Affected versions

< 0.17.8

Patched versions

0.17.8

Description

Impact

An authenticated user could invoke actions that an operator had excluded through action configuration. Existing action permissions and downstream authorization remain enforced.

Patches

Patched in @backstage/backend-defaults version 0.17.8

Workarounds

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

References

@freben freben published to backstage/backstage Aug 28, 2026
Published by the National Vulnerability Database Oct 12, 2026
Published to the GitHub Advisory Database Oct 15, 2026
Reviewed Oct 15, 2026
Last updated Oct 15, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(14th percentile)

Weaknesses

Improper Access Control

The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Learn more on MITRE.

CVE ID

CVE-2026-106495

GHSA ID

GHSA-3xr5-8w6c-p5gw

Source code

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