CVE-2026-106486 in plugin-scaffolder-backend-module-bitbucket-cloud
Summary
by MITRE • 10/07/2026
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.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified involves a path traversal flaw within the Bitbucket integration modules of Backstage, specifically affecting the scaffolder backend components for both Bitbucket Cloud and Bitbucket Server environments. Prior to versions 0.3.10 and 0.2.25 respectively, these plugins failed to adequately sanitize or validate filesystem paths when processing pull request operations initiated through Scaffolder templates. This deficiency allows an authenticated user who possesses the ability to execute eligible scaffolding templates and influence actions within a permitted Bitbucket repository to manipulate file system access controls in unintended ways. The core technical flaw lies in the insufficient validation of path inputs, which permits directory traversal sequences that can escape the designated working area or sandbox intended for template execution.
From an operational perspective, this vulnerability poses significant risks to backend confidentiality, integrity, and availability. By exploiting the lack of proper path normalization, a malicious actor could potentially read sensitive configuration files, overwrite critical application binaries, or delete essential data structures located outside the expected directory boundaries. This capability undermines the isolation guarantees provided by the scaffolder system, effectively allowing an attacker with limited initial privileges to escalate their impact on the underlying infrastructure hosting Backstage services. The ability to write arbitrary files can lead to remote code execution if combined with other vulnerabilities in the deployment pipeline or service configuration, while reading sensitive data could expose secrets such as API keys, database credentials, or internal network topology information stored within accessible directories.
This issue is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory, which describes weaknesses where software does not properly neutralize special elements like dot-dot-slash sequences that can resolve to a parent directory. In the context of attack methodologies, this vulnerability aligns with ATT&CK technique T1083: File and Directory Discovery, as it enables an attacker to enumerate and access files outside their authorized scope. Furthermore, if exploited for writing malicious scripts or binaries into executable paths, it may facilitate lateral movement or persistence mechanisms categorized under techniques such as T1574: Hijack Execution Flow or T1608: Stage Capabilities. The severity of the impact is heightened by the fact that scaffolder templates are often used in automated CI/CD pipelines where trust boundaries between user input and system execution must be strictly enforced to prevent supply chain attacks.
To mitigate this vulnerability, organizations running Backstage environments with affected Bitbucket plugins should immediately upgrade backstage/plugin-scaffolder-backend-module-bitbucket-cloud to version 0.3.10 or later and backstage/plugin-scaffolder-backend-module-bitbucket-server to version 0.2.25 or later. These updates implement rigorous path validation logic that ensures all file operations remain confined within the designated working directory, thereby neutralizing traversal attempts. Additionally, administrators should review existing scaffolder templates for any custom actions that might interact with the file system and ensure they adhere to strict input sanitization practices. Implementing least-privilege principles for service accounts running Backstage backend processes can further limit the potential damage if a similar vulnerability were discovered in other components of the platform. Regular auditing of template permissions and repository access controls remains essential to maintaining a secure developer portal infrastructure.