The cache server in kcp, before versions 0.29.3 and 0.30.3, can be accessed directly from the root shard without any authentication or authorization checks. This flaw allows an attacker who can reach the root shard to read from or write to the cache, effectively compromising data confidentiality and integrity. Exploitation requires only network connectivity to the root shard, with no additional privileges needed.

kcp, a Kubernetes‑like control plane developed by kcp‑dev, is affected. All releases prior to 0.29.3 and prior to 0.30.3 expose the vulnerability. This includes kcp 0.29.x up to 0.29.2 and kcp 0.30.x up to 0.30.2.

The vulnerability carries a CVSS base score of 8.2, categorizing it as high severity. The exploit probability is not quantified, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog. The likely attack vector is network‑based, requiring access to the root shard. Because no authentication is enforced, any party that can contact the root shard can immediately exploit the flaw, making it a significant risk for environments that expose kcp to external networks.