CVE-2021-41151

Path Traversal in @backstage/plugin-scaffolder-backend

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A malicious actor could read sensitive files from the environment where Scaffolder tasks are run. The attack is executed by crafting a custom Scaffolder template with a publish:github:pull-request action using a particular source path. When the template is executed the sensitive files would be included in the published pull request.

This vulnerability is mitigated by the fact that an attacker would need access to create and register templates in the Backstage catalog, and that the attack is very visible given that the exfiltration happens via a pull request.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2021-41151 has a CVSS score of 6.8 (Medium). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.15.9); upgrading removes the vulnerable code path.

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The vulnerability is patched in the 0.15.9 release of @backstage/plugin-scaffolder-backend.

1. What is CVE-2021-41151? CVE-2021-41151 is a medium-severity path traversal vulnerability in @backstage/plugin-scaffolder-backend (npm), affecting versions >= 0.9.4, < 0.15.9. It is fixed in 0.15.9. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2021-41151? CVE-2021-41151 has a CVSS score of 6.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @backstage/plugin-scaffolder-backend are affected by CVE-2021-41151? @backstage/plugin-scaffolder-backend (npm) versions >= 0.9.4, < 0.15.9 is affected.
4. Is there a fix for CVE-2021-41151? Yes. CVE-2021-41151 is fixed in 0.15.9. Upgrade to this version or later.
5. Is CVE-2021-41151 exploitable, and should I be worried? Whether CVE-2021-41151 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-41151 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-41151? Upgrade @backstage/plugin-scaffolder-backend to 0.15.9 or later.

Other vulnerabilities in @backstage/plugin-scaffolder-backend