GHSA-3vcp-chfh-f6r2 Default kuma-cp leaks admin token cross-origin via CORS wildcard + LocalhostIsAdmin

• Go github.com/kumahq/kuma: < 2.7.25 → fixed in 2.7.25 • Go github.com/kumahq/kuma: >= 2.9.0, < 2.9.15 → fixed in 2.9.15 • Go github.com/kumahq/kuma: >= 2.11.0, < 2.11.13 → fixed in 2.11.13 • Go github.com/kumahq/kuma: >= 2.12.0, < 2.12.10 → fixed in 2.12.10 • Go github.com/kumahq/kuma: >= 2.13.0, < 2.13.5 → fixed in 2.13.5

Summary Default `kuma-cp` config leaks the admin bootstrap token and signing keys to any webpage the operator visits while the control plane is reachable from their browser. `CorsAllowedDomains: [".*"]` reflects any `Origin`, and `LocalhostIsAdmin: true` promotes requests from `127.0.0.1` to `mesh-system:admin`. A cross-origin `fetch()` from a malicious page returns the admin JWT and signing material. Am I affected? You are affected if all of these hold: 1. `kuma-cp` runs with default config (`CorsAllowedDomains: [".*"]` and `LocalhostIsAdmin: true`). 2. The control plane is reachable from a browser on the same machine: • `kuma-cp run` on a developer laptop • Docker `--network host` or port-publish on a workstation • `kubectl port-forward` from a machine that also browses the web 3. The operator visits a page running attacker JavaScript while the control plane is reachable. You are not affected if: • The control plane runs on a Kubernetes cluster accessed via ClusterIP, NodePort, or LoadBalancer from a remote client. • The control plane runs on an SSH-administered VM with no browser on the host. • `KUMA_API_SERVER_AUTHN_LOCALHOST_IS_ADMIN=false` is set (see https://kuma.io/docs/latest/production/secure-deployment/api-server-auth/). • `KUMA_API_SERVER_CORS_ALLOWED_DOMAINS` is set to an explicit allowlist that excludes attacker origins. Mitigation 1. Set `KUMA_API_SERVER_AUTHN_LOCALHOST_IS_ADMIN=false` after retrieving the admin token. 2. Set `KUMA_API_SERVER_CORS_ALLOWED_DOMAINS` to an explicit allowlist, for example `http://localhost:5681,http://127.0.0.1:5681`. 3. Do not run `kuma-cp` on a machine where you browse untrusted sites. Fix Fixed in #16416, backported to all supported release branches (#16423, #16424, #16425, #16426, #16427). Changes in patched versions: • `CorsAllowedDomains` default changed from `[".*"]` to `[]` — CORS is now opt-in; set the env var explicitly if you need GUI access. • `LocalhostIsAdmin` hardened: now requires direct loopback `RemoteAddr` and `Host`, and rejects requests carrying proxy-hop headers (`X-Forwarded-For`), cross-site fetch metadata (`Sec-Fetch-Site`), or a non-localhost `Origin`. Upgrade to a patched version: • 2.7.25 • 2.9.15 • 2.11.13 • 2.12.10 • 2.13.5 Credits Reported by `eldudareeno`. CVSS `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N` = 5.1 Medium.