CVE-2021-4178 — kubernetes-client
MEDIUMCVE-2021-4178 is a medium-severity (CVSS 6.7) Deserialization of Untrusted Data vulnerability in io.fabric8:kubernetes-client. A fix is available for io.fabric8:kubernetes-client — see the affected versions and patch details below.
fabric8 kubernetes-client vulnerable
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-2021-4178 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 377,166 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
io.fabric8:kubernetes-client☕io.fabric8:kubernetes-client☕io.fabric8:kubernetes-client☕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 arbitrary code execution flaw was found in the Fabric 8 Kubernetes client affecting versions 5.0.0-beta-1 and above. Due to an improperly configured YAML parsing, this will allow a local and privileged attacker to supply malicious YAML.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.fabric8:kubernetes-client | ≥ 5.0.0-beta-1&&< 5.0.3 | 5.0.3io.fabric8:kubernetes-client:5.0.3 |
| ☕Maven | io.fabric8:kubernetes-client | ≥ 5.1.0&&< 5.1.2 | 5.1.2io.fabric8:kubernetes-client:5.1.2 |
| ☕Maven | io.fabric8:kubernetes-client | ≥ 5.2.0&&< 5.3.2 | 5.3.2io.fabric8:kubernetes-client:5.3.2 |
| ☕Maven | io.fabric8:kubernetes-client | ≥ 5.5.0&&< 5.7.4 | 5.7.4io.fabric8:kubernetes-client:5.7.4 |
| ☕Maven | io.fabric8:kubernetes-client | ≥ 5.8.0&&< 5.8.1 | 5.8.1io.fabric8:kubernetes-client:5.8.1 |
| ☕Maven | io.fabric8:kubernetes-client | ≥ 5.9.0&&< 5.10.2 | 5.10.2io.fabric8:kubernetes-client:5.10.2 |
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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.fabric8:kubernetes-client to 5.0.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-4178 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-2021-4178 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-4178. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Red Hat CodeReady Studio 12 is not affected by this flaw because it does not ship a vulnerable version of kubernetes-client; the version that it ships does not use SnakeYAML.
| Product | Fixed in | Advisory |
|---|---|---|
| OCP-Tools-4.13-RHEL-8 | jenkins-2-plugins-0:4.13.1684911916-1.el8 | RHSA-2023:3299 |
| Red Hat AMQ Streams 1.6.7 | see advisory | RHSA-2022:0467 |
| Red Hat AMQ Streams 2.0.1 | kubernetes-client | RHSA-2022:0469 |
| Red Hat build of Quarkus 2.2.5 | kubernetes-client | RHSA-2022:0589 |
| Red Hat Fuse 7.11 | kubernetes-client | RHSA-2022:5532 |
| RHINT Camel-Q 2.2.1 | see advisory | RHSA-2022:1013 |
| Text-Only RHOAR | kubernetes-client | RHSA-2022:8761 |
Frequently Asked Questions
Is CVE-2021-4178 in your dependencies?
O3 Security finds CVE-2021-4178 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.