CVE-2020-15228 — @actions/core
LOWCVE-2020-15228 is a low-severity (CVSS 3.5) Improper Input Validation vulnerability in @actions/core. 3 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for @actions/core — see the affected versions and patch details below.
Environment Variable Injection in GitHub Actions
EPSS Exploitation Probability
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
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.
@actions/corenpmDescription
Impact
The @actions/core npm module addPath and exportVariable functions communicate with the Actions Runner over stdout by generating a string in a specific format. Workflows that log untrusted data to stdout may invoke these commands, resulting in the path or environment variables being modified without the intention of the workflow or action author.
Patches
The runner will release an update that disables the set-env and add-path workflow commands in the near future. For now, users should upgrade to @actions/core v1.2.6 or later, and replace any instance of the set-env or add-path commands in their workflows with the new Environment File Syntax. Workflows and actions using the old commands or older versions of the toolkit will start to warn, then error out during workflow execution.
Workarounds
None, it is strongly suggested that you upgrade as soon as possible.
For more information
If you have any questions or comments about this advisory:
- Open an issue in Actions Toolkit
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @actions/core | all versions | 1.2.6npm install @actions/core@1.2.6 |
Affected Products
toolkittoolkit_projectResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @actions/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @actions/core to 1.2.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15228 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.
Frequently Asked Questions
Is CVE-2020-15228 in your dependencies?
Find it across npm, including transitive dependencies.