simple-git: VISUAL Editor Fallback Bypasses Unsafe-Editor Protection in @simple-git/argv-parser

A security advisory (GHSA-v5rq-49vh-5v5c, tracked as CVE-2026-102829) reports a control-bypass flaw in @simple-git/argv-parser, the package simple-git uses to detect unsafe editor environment variables before spawning Git. According to the report, the parser's GitEnvKeys denylist classifies EDITOR, GIT_EDITOR, and GIT_SEQUENCE_EDITOR as allowUnsafeEditor risks, but omits VISUAL — a variable Git also consults, and which takes precedence over EDITOR in Git's own resolution order. Because the parser's filtering logic only retains keys it already recognizes, a VISUAL value is dropped before any check runs, so vulnerabilityCheck() returns no findings and simple-git's blockUnsafeOperationsPlugin allows the Git child process to spawn.

Why It Matters

This affects any application using simple-git's default unsafe-operations guard that forwards attacker-influenced environment values into Git calls. If an attacker can control an environment variable that ends up passed to Git (directly or via a request/job pipeline), setting VISUAL to a malicious path achieves the same outcome the guard exists to prevent for EDITOR/GIT_EDITOR: on commands that open an editor — such as git commit --amend or git rebase -i — Git executes the attacker-chosen binary as the host user, operating against files like .git/COMMIT_EDITMSG or the rebase-todo file. No special configuration or opt-in is required; the report states this was reproduced against default options with no unsafe allowances enabled. A public PoC is noted as available.

What Defenders Should Watch For

• Inventory where your application or CI/CD pipelines use simple-git (or raw Git child processes) with environment values derived from user input, webhooks, or job parameters — especially before commit, commit --amend, or rebase -i operations.
• Treat VISUAL the same as EDITOR/GIT_EDITOR: audit and sanitize it anywhere environment variables are forwarded into Git child processes, rather than relying solely on the library's built-in guard.
• Hunt for unexpected child processes spawned by git (particularly short-lived helper scripts) during commit/rebase operations on hosts or build agents where environment input isn't tightly controlled.
• Consider explicitly setting GIT_EDITOR or core.editor in environments where Git invokes an editor programmatically, since both take precedence over VISUAL and would neutralize this gap even before a patch is applied.
• Track upstream for a fix adding VISUAL (and watch for related discussion of TERM, which the report notes also isn't classified and controls whether Git consults VISUAL at all).

This is developing intel based on a newly published advisory; details on patch availability may evolve. Review the full technical writeup and proof-of-concept at the original GHSA advisory.