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.
{
"extracted_events": [
{
"cpe": "cpe:2.3:a:kubernetes:kubernetes:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"last_affected": "1.18.18"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:kubernetes:kubernetes:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "1.19.0"
},
{
"last_affected": "1.19.10"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:kubernetes:kubernetes:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "1.20.0"
},
{
"last_affected": "1.20.6"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:kubernetes:kubernetes:1.21.0:*:*:*:*:*:*:*",
"range": [
{
"introduced": "1.21.0"
},
{
"last_affected": "1.21.0"
}
],
"source": "CPE_STRING"
}
]
}