CVE-2026-33646

Mise Vulnerable to Arbitrary Code Execution via Tera Templates in .tool-versions Files (Trust Bypass)

Published

2026-06-22

Modified

2026-07-21

EPSS percentile

49%

Aliases

GHSA-fjj5-v948-whjj

Sources

github-advisory

Summary

## Summary Mise processes `.tool-versions` files through the Tera template engine during parsing, with the `exec()` function registered, enabling arbitrary command execution. Unlike `.mise.toml` files, `.tool-versions` files are **not subject to trust verification** in non-paranoid mode. This means an attacker can place a malicious `.tool-versions` file in a git repository, and when a victim with mise activated `cd`s into the directory, arbitrary commands execute without any trust prompt. ## Vulnerability Details ### Vulnerable Code **File:** `src/config/config_file/tool_versions.rs`, lines 60-63 ```rust pub fn parse_str(s: &str, path: PathBuf) -> Result { let mut cf = Self::init(&path); let dir = path.parent(); let s = get_tera(dir).render_str(s, &cf.context)?; // ) -> 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 } ``` **File:** `src/tera.rs`, lines 394-452 -- `tera_exec` passes the `command` argument to a shell for execution with no restrictions. **File:** `src/config/config_file/mod.rs`, lines 272-287 ```rust pub async fn parse(path: &Path) -> Result > { if let Ok(settings) = Settings::try_get() && settings.paranoid { trust_check(path)?; // Only in paranoid mode! } match detect_config_file_type(path).await { // ... Some(ConfigFileType::ToolVersions) => Ok(Arc::new(ToolVersions::from_file(path)?)), // ... } } ``` ### Attack Vector 1. An attacker creates a `.tool-versions` file in a git repository containing Tera template syntax with the `exec()` function. 2. The victim clones the repository and has mise activated in their shell (via `eval "$(mise activate zsh)"` or equivalent). 3. When the victim `cd`s into the repository directory, mise's shell hook (`hook-env`) fires automatically. 4. `hook-env` loads and parses config files, including `.tool-versions`. 5. During parsing, `ToolVersions::parse_str` processes the file content through `get_tera(dir).render_str()`. 6. The Tera engine evaluates `{{ exec(command="...") }}`, executing arbitrary commands as the victim's user. 7. No trust prompt is displayed because `trust_check` is not called for `.tool-versions` files in non-paranoid mode. ### Execution Context - Commands execute as the current user with full access to their environment. - The pristine environment (`env::PRISTINE_ENV`) is passed to the executed command, which includes all of the user's environment variables (potentially including tokens, credentials, SSH agents, etc.). - Execution happens silently during the prompt hook -- the user sees no indication that code was run. ### Contrast with .mise.toml `.mise.toml` files are protected: `MiseToml::from_str()` calls `trust_check(path)` before any parsing occurs (line 213 of `mise_toml.rs`). During `hook-env`, untrusted `.mise.toml` files fail to parse with an `UntrustedConfig` error, preventing any code execution. `.tool-versions` files lack this protection entirely. ## Steps to Reproduce ### Prerequisites - mise installed (`brew install mise` or equivalent) - Shell activation enabled: `eval "$(mise activate zsh)"` (or bash/fish) - Default settings (paranoid mode NOT enabled — this is the default) ### PoC: Silent RCE on `cd` **Step 1:** Create a directory simulating a cloned repository with a malicious `.tool-versions`: ```bash mkdir -p /tmp/poc-mise-repo cd /tmp/poc-mise-repo git init cat > .tool-versions /tmp/mise-rce-proof && echo SUCCESS=$(whoami) >> /tmp/mise-rce-proof && date >> /tmp/mise-rce-proof") }}node 20.0.0 python 3.11.0 EOF git add -A && git commit -m "Initial commit" ``` Note: The `exec()` output is c

Affected packages

Remediation: Upgrade to 2026.3.10 or later.

References

• https://github.com/advisories/GHSA-fjj5-v948-whjj