CVE-2021-25741 — kubernetes
HIGHCVE-2021-25741 is a high-severity (CVSS 8.1) Improper Input Validation vulnerability in k8s.io/kubernetes. 2 public exploit references exist, so weaponization risk is real. A fix is available for k8s.io/kubernetes — see the affected versions and patch details below.
Files or Directories Accessible to External Parties in kubernetes
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2021-25741.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-25741 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
k8s.io/kubernetes🐹k8s.io/kubernetes🐹k8s.io/kubernetes🐹k8s.io/kubernetesReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
A security issue was discovered in Kubernetes where a user may be able to create a container with subpath volume mounts to access files & directories outside of the volume, including on the host filesystem.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | k8s.io/kubernetes | all versions | 1.19.15go get k8s.io/kubernetes@v1.19.15 |
| 🐹Go | k8s.io/kubernetes | ≥ 1.20.0&&< 1.20.11 | 1.20.11go get k8s.io/kubernetes@v1.20.11 |
| 🐹Go | k8s.io/kubernetes | ≥ 1.21.0&&< 1.21.5 | 1.21.5go get k8s.io/kubernetes@v1.21.5 |
| 🐹Go | k8s.io/kubernetes | ≥ 1.22.0&&< 1.22.2 | 1.22.2go get k8s.io/kubernetes@v1.22.2 |
Affected Products
kuberneteskubernetesResearch 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 k8s.io/kubernetes, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update k8s.io/kubernetes to 1.19.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-25741 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.
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.
OpenShift Container Platform runs with SELinux in enforcing mode, which reduces the impact of this vulnerability, but does not completely prevent it from being exploited.Source: Red Hat security advisory for CVE-2021-25741 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat OpenShift Container Platform 3.11 | atomic-openshift-0:3.11.524-1.git.0.2dffce7.el7 | RHSA-2021:3646 |
| Red Hat OpenShift Container Platform 4.6 | openshift-0:4.6.0-202109180038.p0.git.d5ed12c.assembly.stream.el7 | RHSA-2021:3642 |
| Red Hat OpenShift Container Platform 4.7 | openshift-0:4.7.0-202109172126.p0.git.bbbc079.assembly.stream.el7 | RHSA-2021:3635 |
| Red Hat OpenShift Container Platform 4.8 | openshift-0:4.8.0-202109180335.p0.git.a620f50.assembly.stream.el7 | RHSA-2021:3631 |
Frequently Asked Questions
Is CVE-2021-25741 in your dependencies?
Find it across Go, including transitive dependencies.