The problem is that the Fission router automatically registers internal‑style routes for every function object, even if no HTTPTrigger is defined for that function. These routes are exposed on the public listener (svc/router, port 8888) that also serves user‑defined triggers. An external requester can call /fission‑function/<namespace>/<name> and invoke any function simply by knowing its metadata name. Because the request bypasses the host, path, method, and method‑allow‑list restrictions encoded in HTTPTrigger objects, attackers can execute code in the function’s runtime environment without being authenticated or authorized. This translates to a high‑severity remote code execution risk.

Affected deployments are those running the Fission framework version 1.22.x or earlier, which automatically expose all functions on the public router. The vulnerability applies to the fission:fission product across all namespaces. Any deployment that has functions exposed by this router is at risk until the patch is applied.

The CVSS score of 9.8 indicates critical severity, and the EPSS score is not available, so the current exploit probability is unknown. The vulnerability is not listed in the CISA KEV catalog. The likely attack vector is via the public router listener; any external entity that can reach the router can invoke the function. No specific authentication or privilege levels are required, meaning that even unauthenticated traffic could exploit the flaw. The exposed endpoint permits unrestricted code execution within the function’s runtime, which could compromise the underlying Kubernetes cluster if the function uses privileged resources.