CVE-2026-68518

Summary

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.

Affected versions

glances <= 4.5.5 (verified against the published PyPI release 4.5.5, the latest at the time of writing; glances.__version__ == "4.5.5"). The per-field sanitizer _sanitize_mustache_dict() is present and active in this release. Not patched in any released version.

Privilege required

Two roles are involved:

• A local, unprivileged user (or a container the attacker can name) supplies the attacker-controlled stat values (process/container name, mount point, etc.). This is the same trust boundary the action-template command-injection class already recognises: the attacker controls the process name, not the configuration.
• An administrator has configured an action whose command template concatenates two unescaped Mustache variables with no separating character ({{{name}}}{{{cmdline}}}). Unescaped Mustache ({{{ }}} / {{& }}) is a documented Chevron feature and is the natural choice when the operator wants a value that contains shell-significant characters to reach the command verbatim.

No network access to the target host is required beyond the ability to run a process (or start a named container) on it.

Vulnerable code (file:line)

glances/actions.py:25-46 — the per-field sanitizer:

# glances/actions.py:25
_SHELL_OPERATORS = ('&&', '|', '>>', '>')

def _sanitize_mustache_dict(mustache_dict):
    """Return a copy of mustache_dict with shell operators replaced by spaces."""
    if not mustache_dict:
        return mustache_dict
    safe = {}
    for k, v in mustache_dict.items():
        if isinstance(v, str):
            for op in _SHELL_OPERATORS:
                v = v.replace(op, ' ')          # per-field only
            safe[k] = v
        else:
            safe[k] = v
    return safe

glances/actions.py:100-111 — sanitize-then-render-then-execute:

# glances/actions.py:100
for cmd in commands:
    if chevron_tag:
        safe_dict = _sanitize_mustache_dict(mustache_dict)
        cmd_full = chevron.render(cmd, safe_dict)   # concatenation happens here
    else:
        cmd_full = cmd
    ret = secure_popen(cmd_full)                    # operators interpreted

Root cause

_sanitize_mustache_dict() removes &&, |, >>, > from each value in isolation. It does not remove a lone &, because a single & is not one of the listed operators. When two values are rendered next to each other by chevron.render(), a trailing & from the first value and a leading & from the second value join into a literal && in cmd_full. secure_popen() then cmd.split('&&') and runs the second half as a separate subprocess.Popen (shell=False) process. The same reconstruction works for > written as two…

Summary

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.

Affected versions

glances <= 4.5.5 (verified against the published PyPI release 4.5.5, the latest at the time of writing; glances.__version__ == "4.5.5"). The per-field sanitizer _sanitize_mustache_dict() is present and active in this release. Not patched in any released version.

Privilege required

Two roles are involved:

• A local, unprivileged user (or a container the attacker can name) supplies the attacker-controlled stat values (process/container name, mount point, etc.). This is the same trust boundary the action-template command-injection class already recognises: the attacker controls the process name, not the configuration.
• An administrator has configured an action whose command template concatenates two unescaped Mustache variables with no separating character ({{{name}}}{{{cmdline}}}). Unescaped Mustache ({{{ }}} / {{& }}) is a documented Chevron feature and is the natural choice when the operator wants a value that contains shell-significant characters to reach the command verbatim.

No network access to the target host is required beyond the ability to run a process (or start a named container) on it.

Vulnerable code (file:line)

glances/actions.py:25-46 — the per-field sanitizer:

# glances/actions.py:25
_SHELL_OPERATORS = ('&&', '|', '>>', '>')

def _sanitize_mustache_dict(mustache_dict):
    """Return a copy of mustache_dict with shell operators replaced by spaces."""
    if not mustache_dict:
        return mustache_dict
    safe = {}
    for k, v in mustache_dict.items():
        if isinstance(v, str):
            for op in _SHELL_OPERATORS:
                v = v.replace(op, ' ')          # per-field only
            safe[k] = v
        else:
            safe[k] = v
    return safe

glances/actions.py:100-111 — sanitize-then-render-then-execute:

# glances/actions.py:100
for cmd in commands:
    if chevron_tag:
        safe_dict = _sanitize_mustache_dict(mustache_dict)
        cmd_full = chevron.render(cmd, safe_dict)   # concatenation happens here
    else:
        cmd_full = cmd
    ret = secure_popen(cmd_full)                    # operators interpreted

Root cause

_sanitize_mustache_dict() removes &&, |, >>, > from each value in isolation. It does not remove a lone &, because a single & is not one of the listed operators. When two values are rendered next to each other by chevron.render(), a trailing & from the first value and a leading & from the second value join into a literal && in cmd_full. secure_popen() then cmd.split('&&') and runs the second half as a separate subprocess.Popen (shell=False) process. The same reconstruction works for > written as two…

Glances is an open-source system cross-platform monitoring tool. Prior to 4.5.6, _sanitize_mustache_dict() in glances/actions.py sanitizes individual Mustache values before chevron.render(), allowing adjacent unescaped Mustache variables to reconstruct shell operators that secure_popen() executes when attacker-controlled process or container fields are rendered by an administrator-configured action template. This issue is fixed in 4.5.6.

These are all security issues fixed in the glances-common-4.5.6-1.1 package on the GA media of openSUSE Tumbleweed.