CVE-2026-67438

### Summary OliveTin's checkShellArgumentSafety() function maintains a blocklist of argument types unsafe for Shell mode actions, but does not include regex:-prefixed types. Because regex: support was added independently via typeSafetyCheckRegex(), any Shell mode action using a regex:-typed argument bypasses the safety check unconditionally. The unvalidated value is then interpolated directly into the sh -c command string via Go's text/template with no escaping, enabling shell injection. Notably, even restrictive-looking patterns are exploitable — for example, a pattern blocking common shell metacharacters remains bypassable via POSIX command substitution. ### Details OliveTin is an open source web UI for running pre-configured shell commands. In the OliveTin service component, the function checkShellArgumentSafety() in service/internal/executor/arguments.go enforces a blocklist of argument types that are unsafe for use in Shell mode actions (actions that execute via sh -c). The blocklist includes password, very_dangerous_raw_string, url, email, and raw_string_multiline. It does not handle custom regex: prefixed argument types. Custom regex: types are supported by a separate function, typeSafetyCheckRegex(), which checks whether a submitted value matches the provided pattern. These two functions evolved independently: when regex: prefix support was added to typeSafetyCheckRegex, checkShellArgumentSafety was not updated to treat regex: types as unsafe for Shell mode. As a result, any action configured with a Shell mode handler and a regex:-typed argument passes the safety check unconditionally, regardless of how permissive or restrictive the pattern is. The argument value then reaches handleShellBranch → wrapCommandInShell, where Go's text/template interpolates it directly into the sh -c command string with no escaping. Critically, this vulnerability is not limited to obviously permissive patterns like regex:.*. An admin who writes a restrictive-looking pattern s