CVE-2026-52831: Nuclio: Unsanitized cron trigger event headers/body injected into CronJob shell command leads to persistent RCE

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 — interpolated verbatim inside double-quoted --header arguments (lazy.go:2150); any key containing " breaks the quoting context.
• event.body — processed with strconv.Quote, which escapes " and \ but not $(), allowing command substitution (lazy.go:2188).

Both paths were dynamically verified on Nuclio 1.15.27 (latest as of 2026-05-17).

• CVSS 3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H — 9.9 (Critical)
• CWE: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)
• Affected versions: Nuclio <= 1.15.27 (latest, dynamically verified)