CVE-2021-25737: Holes in EndpointSlice Validation Enable Host Network Hijack
First published: Thu Apr 29 2021(Updated: )
A security issue was discovered in Kubernetes where a user may be able to redirect pod traffic to private networks on a Node. Kubernetes already prevents creation of Endpoint IPs in the localhost or link-local range, but the same validation was not performed on EndpointSlice IPs.
Credit: jordan@liggitt.net
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Kubernetes Kubernetes | >=1.16.0<1.18.19 | |
| Kubernetes Kubernetes | >=1.19.0<1.19.10 | |
| Kubernetes Kubernetes | >=1.20.0<1.20.7 | |
| Kubernetes Kubernetes | =1.21.0 | |
| redhat/openshift | <0:4.8.0-202107161820.p0.git.051ac4f.assembly.stream.el8 | 0:4.8.0-202107161820.p0.git.051ac4f.assembly.stream.el8 |
Remedy
* Prevent untrusted users from creating or modifying EndpointSlices * Creating a validating admission webhook that prevents EndpointSlices with endpoint addresses in the 127.0.0.0/8 and 169.254.0.0/16 ranges
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Reference Links
- https://github.com/kubernetes/kubernetes/issues/102106
- https://groups.google.com/g/kubernetes-security-announce/c/xAiN3924thY
- https://security.netapp.com/advisory/ntap-20211004-0004/
- https://github.com/kubernetes/kubernetes/pull/101084
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1962296
- https://access.redhat.com/errata/RHSA-2021:2437
- https://access.redhat.com/security/cve/cve-2021-25737
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1954917#c14
- https://bugzilla.redhat.com/show_bug.cgi?id=1954917
- https://www.cve.org/CVERecord?id=CVE-2021-25737 https://nvd.nist.gov/vuln/detail/CVE-2021-25737 https://github.com/kubernetes/kubernetes/issues/102106 https://groups.google.com/g/kubernetes-security-announce/c/xAiN3924thY
Frequently Asked Questions
What is the severity of CVE-2021-25737?
The severity of CVE-2021-25737 is medium.
How can an authorized user exploit CVE-2021-25737?
An authorized user can exploit CVE-2021-25737 by redirecting pod traffic to private networks on a Node.
What software versions are affected by CVE-2021-25737?
The following software versions are affected by CVE-2021-25737: Kubernetes 1.21.1, Kubernetes 1.20.7, Kubernetes 1.19.11, Kubernetes 1.18.19, OpenShift 4.8.0-202107161820.p0.git.051ac4f.assembly.stream.el8.
How do I fix CVE-2021-25737?
To fix CVE-2021-25737, update your Kubernetes or OpenShift software to the appropriate remediation version: Kubernetes 1.21.1, Kubernetes 1.20.7, Kubernetes 1.19.11, Kubernetes 1.18.19, OpenShift 4.8.0-202107161820.p0.git.051ac4f.assembly.stream.el8.
Where can I find more information about CVE-2021-25737?
You can find more information about CVE-2021-25737 at the following references: [1] GitHub: https://github.com/kubernetes/kubernetes/pull/101084 [2] Red Hat Bugzilla: https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1962296 [3] Red Hat Advisory: https://access.redhat.com/errata/RHSA-2021:2437
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