CVE-2020-8554

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Moderate Moderate Impact What does this mean?
6.3 CVSS v3 Base Score

Description

A flaw was found in kubernetes. If a potential attacker can already create or edit services and pods, then they may be able to intercept traffic from other pods (or nodes) in the cluster.

Statement

OpenShift Container Platform (OCP) includes a builtin externalIP admission plugin, which restricts the use of Service eternalIPs to those configured by a cluster-admin. In OCP4 all externalIP ranges are disabled by default. In OCP 3.11, the default range is "0.0.0.0/0", which allows all IP addresses.

The second attack vector, via patching the Status of a LoadBalancer Service, is not possible unless permission to patch service/status is granted. OCP does not grant this permission to users who are not cluster-admins.

OCP 4 is not affected by this vulnerability as it is secure by default. OCP 3.11 is affected, however the vulnerability can be by mitigated by configuring the builtin externalIP admission plugin.

Mitigation

ExternalIP addresses ranges can be configured as described below. OCP 4 is secure by default, though cluster-admins can whitelist externalIP addresses as needed. OCP 3.11 can be secured by changing `externalIPNetworkCIDR` to "0.0.0.0/32", which blocks all externalIP address values.

https://docs.openshift.com/container-platform/4.6/networking/configuring_ingress_cluster_traffic/configuring-externalip.html
This page is not included, but the link has been rewritten to point to the nearest parent document.https://docs.openshift.com/container-platform/3.11/admin_guide/tcp_ingress_external_ports.html#service-externalip

Users can check if they have permission to patch the Status of a LoadBalancer Service with the command: `kubectl auth can-i patch service --subresource=status`. In OCP, by default only cluster-admins are granted this permission.

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2020-8554

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2020-8554

Content from blog.champtar.fr is not included.https://blog.champtar.fr/K8S_MITM_LoadBalancer_ExternalIPs/

Content from groups.google.com is not included.https://groups.google.com/g/kubernetes-security-announce/c/iZWsF9nbKE8

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Red Hat OpenShift Container Platform 3.11 atomic-openshift Fixed RHSA-2021:0079
Red Hat OpenShift Container Platform 4 openshift Not affected
Red Hat Storage 3 heketi Not affected
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown Red Hat NVD
CVSS v3 Base Score 6.3 5
Attack Vector Network Network
Attack Complexity Low High
Privileges Required Low Low
User Interaction None None
Scope Unchanged Unchanged
Confidentiality Impact Low Low
Integrity Impact Low Low
Availability Impact Low Low

CVSS v3 Vector

Red Hat CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

NVD CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

Red Hat CVSS v3 Score Explanation

Proposed changes to NIST's current CVSSv3 scoring: AC:H -> AC:L C:H -> C:L I:H -> I:L A:H -> A:L

To successfully exploit this vulnerability a potential attacker needs access to create or edit services and pods and then they may be able to intercept traffic from other pods or even cluster nodes. Hence proposing a change to Attack Complexity (AC) from High to Low. Access to some restricted information can be obtained, but the attacker does not have control over what information is obtained. The same situation is in regards to the possible data modification, the attacker does not have control over the consequence of a modification. The attacker also does not have the ability to completely deny service. The Confidentiality, Integrity and Availability (CIA) metrics should be changed from High to Low.

Acknowledgements

Red Hat would like to thank the Kubernetes Product Security Committee for reporting this issue. Upstream acknowledges Etienne Champetier (Anevia) as the original reporter.

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.