CVE-2026-106486: Backstage: Improper filesystem validation in Bitbucket pull-request scaffolder actions

Severity: critical (CVSS 9.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-06 · updated 2026-10-23
Weakness: CWE-22

Description

Backstage is an open framework for building developer portals. Prior to 0.3.10 in @backstage/plugin-scaffolder-backend-module-bitbucket-cloud and 0.2.25 in @backstage/plugin-scaffolder-backend-module-bitbucket-server, the Bitbucket pull-request Scaffolder actions did not sufficiently validate filesystem paths. An authenticated user who can execute an eligible template and influence an allowed Bitbucket repository could affect paths outside the expected working area, potentially compromising backend confidentiality, integrity, or availability. This issue is fixed in @backstage/plugin-scaffolder-backend-module-bitbucket-cloud 0.3.10 and @backstage/plugin-scaffolder-backend-module-bitbucket-server 0.2.25.

Affected products

backstage: before 1.54.6 — fixed in 1.54.6
Linuxfoundation Backstage/Plugin-Scaffolder-Backend-Module-Bitbucket-Cloud: before 0.3.10 — fixed in 0.3.10
Linuxfoundation Backstage/Plugin-Scaffolder-Backend-Module-Bitbucket-Server: before 0.2.25 — fixed in 0.2.25

How to fix

Upgrade to a fixed version: backstage 1.54.6; Linuxfoundation Backstage/Plugin-Scaffolder-Backend-Module-Bitbucket-Cloud 0.3.10; Linuxfoundation Backstage/Plugin-Scaffolder-Backend-Module-Bitbucket-Server 0.2.25. Check the vendor advisory for mitigations.

References

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