Description

Nuclio is a "Serverless" framework for Real-Time Events and Data Processing. Prior to version 1.16.4, the Nuclio controller builds a curl invocation string for each cron trigger and stores it as the args of a Kubernetes CronJob container (/bin/sh, -c, <command>). Two fields in the trigger specification flow into this string without adequate sanitization: event.headers keys and event.body. This issue has been patched in version 1.16.4.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.0",
  "pubDate": "2026-09-02T17:17:45.347Z",
  "pubdate": "2026-09-02T17:17:45.347Z",
  "executiveSummary": "Nuclio versions prior to 1.16.4 are susceptible to a critical command injection vulnerability stemming from improper input sanitization within the controller component.\nThe vulnerability resides in the processing of cron trigger specifications, specifically when constructing shell commands for Kubernetes CronJob container execution.\nAn unauthenticated or authenticated attacker capable of defining or modifying trigger configurations can inject arbitrary shell commands by crafting malicious event headers or body content.\nSuccessful exploitation allows for remote code execution (RCE) within the context of the CronJob container, potentially leading to unauthorized data access, system disruption, or lateral movement within the Kubernetes cluster.\nThe risk is categorized as high, as it bypasses intended input validation mechanisms during the generation of the shell invocation string (/bin/sh, -c, <command>).\nRemediation requires upgrading the Nuclio controller to version 1.16.4 or later to ensure proper sanitization of trigger arguments.",
  "technicalDetails": "The root cause of this vulnerability is an insecure implementation of command string construction within the Nuclio controller when defining Kubernetes CronJobs. The system dynamically generates command arguments for a shell execution environment by concatenating user-supplied trigger attributes into a string intended to be executed via /bin/sh -c.\nSpecifically, the 'event.headers' keys and the 'event.body' fields are incorporated into the final shell command string without undergoing sufficient sanitization or escaping. This allows an attacker to break out of the intended command context by injecting shell metacharacters such as ';', '&&', '||', or backticks.\nThe attack flow begins when a user creates or updates a cron trigger via the Nuclio API. During the controller's reconciliation loop, it processes the trigger specification. If the specification contains malicious values in the aforementioned fields, the controller constructs a command string that interprets these values as executable shell instructions.\nOnce the CronJob is scheduled by Kubernetes, the container runtime executes the command string via the system shell. Because the shell parses the malicious input as legitimate commands, the attacker gains the ability to execute arbitrary binaries or scripts present in the container image or downloaded during the execution phase.\nThe vulnerability affects all Nuclio versions preceding 1.16.4. The scope of impact is limited to the containerized environment assigned to the CronJob; however, if the container service account possesses excessive RBAC permissions within the Kubernetes cluster, the attacker may escalate their privileges to perform cluster-wide operations.\nNo specific authentication is required if the attacker has permission to define or edit triggers. The attack is triggered upon the execution of the cron job, meaning there may be a temporal delay between the submission of the malicious payload and its execution. This vulnerability highlights the risks associated with constructing shell commands from untrusted inputs in serverless frameworks."
}