Nuclio builds a curl command string for each cron trigger and places the resulting string directly into the arguments of a Kubernetes CronJob container’s shell. Two fields – the event headers keys and the event body – are concatenated into the command without any sanitization, enabling an attacker to inject arbitrary shell commands. The injected commands are executed every time the cron job runs, providing a persistent attack surface. The vulnerability allows remote code execution within the context of the container, potentially giving an attacker unauthorized access and control over the affected system.

Nuclio’s controller, versions prior to 1.16.4. Any deployment that creates cron triggers with custom header or body fields is susceptible. The fix was introduced in release 1.16.4, so installations running an earlier version are impacted.

With a CVSS score of 8, the vulnerability is considered high severity. The EPSS score is not available, so the exact likelihood of exploitation is unknown, but the lack of sanitization means a crafted payload can easily lead to persistent RCE. The vulnerability is not listed in the CISA KEV catalog. The attack vector is most likely a maliciously crafted event sent to the Nuclio controller that expands headers or body values containing shell metacharacters, which are then executed by the cron job shell during its scheduled runs.