GHSA-qh36-44jv-c8xj CVE-2020-8562 GO-2022-0617
Potential proxy IP restriction bypass in Kubernetes
- Severity
- 3.1 / 10
- Low · CVSS 3.1
- Exploit chance (EPSS)
- 1.19%
- Chance of exploitation in the next 30 days. Higher than 67.88% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
- Fix
- None yet
- No fixed version published
Description
As mitigations to a report from 2019 and CVE-2020-8555, Kubernetes attempts to prevent proxied connections from accessing link-local or localhost networks when making user-driven connections to Services, Pods, Nodes, or StorageClass service providers. As part of this mitigation Kubernetes does a DNS name resolution check and validates that response IPs are not in the link-local (169.254.0.0/16) or localhost (127.0.0.0/8) range. Kubernetes then performs a second DNS resolution without validation for the actual connection. If a non-standard DNS server returns different non-cached responses, a user may be able to bypass the proxy IP restriction and access private networks on the control plane. All versions of Kubernetes are impacted, and there is no fix in place.
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| k8s.io/kubernetes | >= 1.21.0, <= 1.21.1 |
No fix yet |
| k8s.io/kubernetes | >= 1.20.0, <= 1.20.7 |
No fix yet |
| k8s.io/kubernetes | >= 1.19.0, <= 1.19.11 |
No fix yet |
| k8s.io/kubernetes | <= 1.18.19 |
No fix yet |
| k8s.io/kubernetes | all versions |
No fix yet |
How to fix
No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.
Severity breakdown
CVSS 3.1 3.1
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Weakness
CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
How to prevent it
- Implementation: The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
- Implementation: When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
- Architecture and Design: Limit the interleaving of operations on files from multiple processes.
- Implementation, Architecture and Design: If you cannot perform operations atomically and you must share access to the resource between multiple processes or threads, then try to limit the amount of time (CPU cycles) between the check and use of the resource. This will not fix the problem, but it could make it more difficult for an attack to succeed.
- Implementation: Recheck the resource after the use call to verify that the action was taken appropriately.
- Architecture and Design: Ensure that some environmental locking mechanism can be used to protect resources effectively.
- Implementation: Ensure that locking occurs before the check, as opposed to afterwards, such that the resource, as checked, is the same as it is when in use.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-r6j8-c6r2-37rr kube-controller-manager is vulnerable to half-blind Server Side Request Forgery through in-tree Portworx StorageClass | Medium | Also affects k8s.io/kubernetes |
| GHSA-4x4m-3c2p-qppc Kubernetes Nodes can delete themselves by adding an OwnerReference | Medium | Also affects k8s.io/kubernetes |
| GHSA-hj2p-8wj8-pfq4 kubernetes allows nodes to bypass dynamic resource allocation authorization checks | Low | Also affects k8s.io/kubernetes |
| GO-2025-3547 Kubernetes kube-apiserver Vulnerable to Race Condition | Low | Also affects k8s.io/kubernetes |
| GHSA-3wgm-2gw2-vh5m Kubernetes GitRepo Volume Inadvertent Local Repository Access | Medium | Also affects k8s.io/kubernetes |
| GHSA-vv39-3w5q-974q Kubernetes allows Command Injection affecting Windows nodes via nodes/*/logs/query API | Medium | Also affects k8s.io/kubernetes |
| GHSA-jgfp-53c3-624w Node Denial of Service via kubelet Checkpoint API | Medium | Also affects k8s.io/kubernetes |
| GHSA-27wf-5967-98gx Kubernetes kubelet arbitrary command execution | High | Also affects k8s.io/kubernetes |
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