CVE-2021-20218
HIGHCVE-2021-20218 is a high-severity (CVSS 7.4) Path Traversal vulnerability in io.fabric8:kubernetes-client. O3 Security confirms whether CVE-2021-20218 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Improper Limitation of a Pathname to a Restricted Directory in Fabric8 Kubernetes Client
Real-World Exposure
io.fabric8:kubernetes-client☕io.fabric8:kubernetes-client☕io.fabric8:kubernetes-client☕io.fabric8:kubernetes-clientReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
A flaw was found in the fabric8 kubernetes-client in version 4.2.0 and after. This flaw allows a malicious pod/container to cause applications using the fabric8 kubernetes-client copy command to extract files outside the working path. The highest threat from this vulnerability is to integrity and system availability. This has been fixed in kubernetes-client-4.13.2 kubernetes-client-5.0.2 kubernetes-client-4.11.2 kubernetes-client-4.7.2
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.fabric8:kubernetes-client | ≥ 4.2.0&&< 4.7.2 | 4.7.2 |
| ☕Maven | io.fabric8:kubernetes-client | ≥ 4.8.0&&< 4.11.2 | 4.11.2 |
| ☕Maven | io.fabric8:kubernetes-client | ≥ 4.12.0&&< 4.13.2 | 4.13.2 |
| ☕Maven | io.fabric8:kubernetes-client | ≥ 5.0.0&&< 5.0.2 | 5.0.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.fabric8:kubernetes-client. 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 io.fabric8:kubernetes-client to 4.7.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-20218 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-2021-20218 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-2021-20218. 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-2021-20218 in your dependencies?
O3 detects CVE-2021-20218 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.