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Date: Mon, 1 Jun 2020 09:04:49 -0700
From: Tim Allclair <>
	"Kubernetes developer/contributor discussion" <>,, 
	kubernetes-security-discuss <>,,
Subject: CVE-2020-8555: Kubernetes: Half-Blind SSRF in kube-controller-manager

Hello Kubernetes Community,

There exists a Server Side Request Forgery (SSRF) vulnerability in
kube-controller-manager that allows certain authorized users to leak up to
500 bytes of arbitrary information from unprotected endpoints within the
master's host network (such as link-local or loopback services).

This issue has been rated medium (
and assigned CVE-2020-8555.
Am I vulnerable?

You may be vulnerable if:


   You are running a vulnerable version (see below);

   There are unprotected endpoints normally only visible from the
   Kubernetes master (including link-local metadata endpoints, unauthenticated
   services listening on localhost, or other services in the master's private
   network); and

   Untrusted users can create pods with an affected volume type or modify
   storage classes.

Affected Versions


   kube-controller-manager v1.18.0

   kube-controller-manager v1.17.0 - v1.17.4

   kube-controller-manager v1.16.0 - v1.16.8

   kube-controller-manager < v1.15.11

The affected volume types are: GlusterFS, Quobyte, StorageFS, ScaleIO
How do I mitigate this vulnerability?

Prior to upgrading, this vulnerability can be mitigated by adding endpoint
protections on the master or restricting usage of the vulnerable volume
types (for example by constraining usage with a PodSecurityPolicy
or third-party admission controller such as Gatekeeper
<>) and restricting
StorageClass write permissions through RBAC.
Fixed Versions

The information leak was patched in the following versions:


   kube-controller-manager v1.18.1+

   kube-controller-manager v1.17.5+

   kube-controller-manager v1.16.9+

   kube-controller-manager v1.15.12+

To upgrade, refer to the documentation:

Further work to protect against SSRF is underway and will be included in an
upcoming patch release (details to follow).
Additional Details

See the GitHub issue for more details:

Thank You,

Tim Allclair on behalf of the Kubernetes Product Security Committee

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