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 references exist, 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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2020-15228 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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 |
Research 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
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2020-15228 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2020-15228. 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-2020-15228 in your dependencies?
O3 Security finds CVE-2020-15228 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.