CVE-2026-52831

Nuclio, an open-source serverless framework for real-time event and data processing on Kubernetes, contains an OS command injection flaw (CWE-78) in how its controller handles cron triggers. Prior to version 1.16.4, the controller interpolates two trigger-configuration fields — event.headers keys and event.body — into a shell command string that is stored as the arguments of a Kubernetes CronJob container (/bin/sh -c), without adequate sanitization, allowing shell metacharacters to break out and execute arbitrary commands. The CVSS vector indicates exploitation requires high privileges (an attacker who can define or modify function trigger specifications) and has high attack complexity, but yields high-impact command execution with a changed scope, meaning code runs in the CronJob pod beyond the intended security boundary. Users running Nuclio versions before 1.16.4 who use cron triggers are affected. There is no known public proof-of-concept, it is not in CISA KEV, and EPSS estimates only a 0.3% probability of exploitation within 30 days.

What to do: Upgrade Nuclio to version 1.16.4 or later, which sanitizes the event.headers keys and event.body fields used in cron trigger command construction. In the meantime, audit existing function configurations for cron triggers whose header keys or body values contain shell metacharacters, and restrict who can create or modify function trigger specifications. Note that exploitation requires high privileges, so limit cluster-level function-management access as an interim mitigation.