CVE-2021-25737: K8s.io/kubernetes Incomplete List Of Disallowed Inputs Vulnerability
MODERATECVE-2021-25737 is a MODERATE (CVSS 4.8) incomplete list of disallowed inputs vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting K8s.io/kubernetes libraries in the Go ecosystem. The issue involves incomplete list of disallowed inputs in kubernetes. Remediation is available by upgrading affected packages to version 1.18.19, 1.19.11, 1.20.7, 1.21.1.
CVE-2021-25737 at a Glance
Security Impact
CVSS: 4.8
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N).
How to Fix CVE-2021-25737
To remediate this vulnerability, upgrade all affected K8s.io/kubernetes dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade k8s.io/kubernetes to 1.18.19Upgrade k8s.io/kubernetes to 1.19.11Upgrade k8s.io/kubernetes to 1.20.7Upgrade k8s.io/kubernetes to 1.21.1Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for k8s.io/kubernetesHow to Check if You Are Affected
To determine whether your application is affected by CVE-2021-25737, inspect your project dependencies for K8s.io/kubernetes:
inspect dependencies for k8s.io/kubernetesAnalyze the terminal output to locate any version of K8s.io/kubernetes in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.18.19), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In K8s.io/kubernetes, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2021-25737 Affected K8s.io/kubernetes Versions
4 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
k8s.io/kubernetes
|
Go |
≥ 1.16.0
< 1.18.19
|
1.18.19
|
|
k8s.io/kubernetes
|
Go |
≥ 1.19.0
< 1.19.11
|
1.19.11
|
|
k8s.io/kubernetes
|
Go |
≥ 1.20.0
< 1.20.7
|
1.20.7
|
|
k8s.io/kubernetes
|
Go |
≥ 1.21.0
< 1.21.1
All 1 versions
1.21.0
|
1.21.1
|
References
Frequently Asked Questions
What is CVE-2021-25737?
Which K8s.io/kubernetes versions are affected?
What version fixes CVE-2021-25737?
Is k8s.io/kubernetes affected?
What is the CVSS score of CVE-2021-25737?
What CWE is associated with CVE-2021-25737?
How can I check Go dependencies for CVE-2021-25737?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-mfv7-gq43-w965",
"modified" : "2021-09-14T18:47:27Z",
"published" : "2021-09-07T23:09:24Z",
"aliases" : [ "CVE-2021-25737" ],
"summary" : "Incomplete List of Disallowed Inputs in Kubernetes",
"details" : "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.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "k8s.io/kubernetes"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.16.0"
}, {
"fixed" : "1.18.19"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "k8s.io/kubernetes"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.19.0"
}, {
"fixed" : "1.19.11"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "k8s.io/kubernetes"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.20.0"
}, {
"fixed" : "1.20.7"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "k8s.io/kubernetes"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.21.0"
}, {
"fixed" : "1.21.1"
} ]
} ],
"versions" : [ "1.21.0" ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-25737"
}, {
"type" : "WEB",
"url" : "https://github.com/kubernetes/kubernetes/issues/102106"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/kubernetes/kubernetes"
}, {
"type" : "WEB",
"url" : "https://groups.google.com/g/kubernetes-security-announce/c/xAiN3924thY"
}, {
"type" : "WEB",
"url" : "https://security.netapp.com/advisory/ntap-20211004-0004"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-184", "CWE-601" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2021-09-07T18:59:14Z",
"nvd_published_at" : "2021-09-06T12:15:00Z"
}
}