The Shell Runtime component of Nuclio accepts a custom HTTP header, X‑Nuclio‑Arguments, which is directly concatenated into shell commands without sanitization. This omission allows an attacker who can send an HTTP request to the function endpoint to inject arbitrary shell instructions, resulting in remote code execution on the host running the Nuclio server. The vulnerability is an instance of command injection originating from insecure handling of user input.

Nuclio, Version 1.15.20 introduced the fix. All versions of Nuclio older than 1.15.20 are affected. The flaw exists within the Nuclio Shell Runtime component that processes HTTP requests to user‑defined serverless functions. Deployments using these older versions are susceptible to exploitation.

The CVSS score of 8.9 indicates a high severity with potential for complete system compromise. The EPSS value of 2 % suggests that, although the flaw is severe, its exploitation frequency remains low, possibly due to a limited attack surface. Nuclio does not list this vulnerability in the CISA KEV catalog, but the lack of exposure does not reduce the risk for an attacker who can reach the vulnerable HTTP endpoint. Exploitation requires the ability to send crafted HTTP requests containing the X‑Nuclio‑Arguments header to an exposed function.