How severe is CVE-2021-43783?

CVE-2021-43783 has a CVSS score of 8.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-43783?

CVE-2021-43783 affects the following packages: @backstage/plugin-scaffolder-backend (npm). Ecosystems affected: npm.

How do I fix CVE-2021-43783?

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.

How do I detect CVE-2021-43783 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @backstage/plugin-scaffolder-backend, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-43783 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2021-43783 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-43783 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-43783?

CVE-2021-43783 has an EPSS (Exploit Prediction Scoring System) score of 1.2%, placing it in the 69th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-43783?

CVE-2021-43783 is classified as Path Traversal (CWE-22). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-43783 published, and has it been updated?

CVE-2021-43783 was published on November 29, 2021 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

HIGH severity

CVE-2021-43783 — @backstage/plugin-scaffol…

HIGHFix: backstage/backstage@f9352ab

CVE-2021-43783 is a high-severity (CVSS 8.5) Path Traversal vulnerability in @backstage/plugin-scaffolder-backend. A fix is available for @backstage/plugin-scaffolder-backend — see the affected versions and patch details below.

Path Traversal in @backstage/plugin-scaffolder-backend

Also known asGHSA-mg3m-f475-28hv

Published

Nov 29, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs69th percentile — riskier than 69% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

69other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@backstage/plugin-scaffolder-backendnpm

197Kdownloads / week

Description

Impact

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.

Patches

This vulnerability is fixed in version 0.15.14 of the @backstage/plugin-scaffolder-backend.

Workarounds

This attack is mitigated by restricting access and requiring reviews when registering or modifying scaffolder templates.

For more information

If you have any questions or comments about this advisory:

Open an issue in the Backstage repository
Visit our chat, linked to in Backstage README

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@backstage/plugin-scaffolder-backend`	all versions	0.15.14`npm install @backstage/plugin-scaffolder-backend@0.15.14`

Affected Products

1 product · 1 configurations

Application

backstagelinuxfoundation

< 0.15.14

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @backstage/plugin-scaffolder-backend, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

### Impact 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. ### Patches This vulnerability is fixed in v