CVE-2021-43783
HIGHCVE-2021-43783 is a high-severity (CVSS 8.5) Path Traversal vulnerability in @backstage/plugin-scaffolder-backend. O3 Security confirms whether CVE-2021-43783 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Path Traversal in @backstage/plugin-scaffolder-backend
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
@backstage/plugin-scaffolder-backendnpmDescription
@backstage/plugin-scaffolder-backend is the backend for the default Backstage software templates. In affected versions a malicious actor with write access to a registered scaffolder template is able to manipulate the template in a way that writes files to arbitrary paths on the scaffolder-backend host instance. This vulnerability can in some situation also be exploited through user input when executing a template, meaning you do not need write access to the templates. This method will not allow the attacker to control the contents of the injected file however, unless the template is also crafted in a specific way that gives control of the file contents. This vulnerability is fixed in version 0.15.14 of the @backstage/plugin-scaffolder-backend. This attack is mitigated by restricting access and requiring reviews when registering or modifying scaffolder templates.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @backstage/plugin-scaffolder-backend | all versions | 0.15.14 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @backstage/plugin-scaffolder-backend. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @backstage/plugin-scaffolder-backend to 0.15.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43783 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-43783 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-43783. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-43783 in your dependencies?
O3 detects CVE-2021-43783 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.