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Potential proxy IP restriction bypass in Kubernetes

Low severity GitHub Reviewed Published Feb 2, 2022 to the GitHub Advisory Database • Updated Aug 6, 2024

Package

gomod k8s.io/kubernetes (Go)

Affected versions

>= 1.21.0, <= 1.21.1
>= 1.20.0, <= 1.20.7
>= 1.19.0, <= 1.19.11
<= 1.18.19

Patched versions

None

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.

References

Published by the National Vulnerability Database Feb 1, 2022
Published to the GitHub Advisory Database Feb 2, 2022
Reviewed Feb 3, 2022
Last updated Aug 6, 2024

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

EPSS score

0.075%
(33rd percentile)

Weaknesses

CVE ID

CVE-2020-8562

GHSA ID

GHSA-qh36-44jv-c8xj

Source code

Credits

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