Kyverno before 1.19.1 is vulnerable to server-side request forgery

Why it is Yellow

• CVSS 7.6 high

References

• https://github.com/kyverno/kyverno/security/advisories/GHSA-q825-p383-r9v5
• https://www.vulncheck.com/advisories/kyverno-before-1.19.1-ssrf-via-legacy-apicall-service-executor

Original description

Kyverno before 1.19.1 is vulnerable to server-side request forgery. The default egress blocklist (169.254.169.254, 169.254.169.253, metadata.google.internal, 127.0.0.0/8, ::1/128) and the scoped-token control were wired only into the new CEL http.Get/Post library and were never applied to the legacy apiCall service executor (pkg/engine/apicall/executor.go) or to the GlobalContextEntry external-API path, which handle every non-CEL context[].apiCall.service call. Because these paths use a plain net/http client with no egress filtering and no validation of the configured service URL, a ClusterPolicy or GlobalContextEntry author — or, where a deployed policy templates the service URL from the admission resource, a lower-privileged resource submitter — can cause Kyverno to issue GET/POST requests to an arbitrary host, including the cloud metadata endpoint, loopback, and any in-cluster service, reading cloud instance credentials and reaching internal endpoints with Kyverno's network position. The executor also unconditionally attaches Kyverno's projected ServiceAccount token to the attacker-chosen destination; the token is audience-scoped, limiting its replay value. Fixed in 1.19.1.