CVE-2026-68518: Glances has a command injection bypass of action-template sanitizer via cross-field shell-operator reconstruction

The Glances action system lets an administrator configure shell commands that run when a monitoring threshold is crossed. The command is a Mustache template whose variables are filled with runtime stat fields such as a process name, a container name or a filesystem mount point. Those fields are attacker-influenceable: a local, unprivileged user who starts a process (or a container) controls its name and command line. The rendered command is executed by secure_popen(), which interprets &&, | and > as chaining / pipe / redirection operators.

glances/actions.py defends against this with _sanitize_mustache_dict(), which strips those operators from each individual template value before rendering. The sanitization is applied per field, but the operators are reconstructed across the boundary of two adjacent template variables after Mustache rendering. When an action template concatenates two unescaped variables ({{{a}}}{{{b}}} or {{&a}}{{&b}}) and the attacker makes the first value end with & and the second begin with &, the rendered command contains a real &&, and secure_popen() executes the injected command. The single-& in each value passes the per-field filter untouched.