PYSEC-2026-1483

## Overview

On many platforms, a third party can create a Git repository under a name that includes a shell command substitution [^1] string in the syntax `$(<command>)`. These directory names are allowed in macOS and a majority of Linux distributions [^2]. If a user starts `jupyter-lab` in a parent directory of this inappropriately-named Git repository, opens it, and clicks "Git > Open Git Repository in Terminal" from the menu bar, then the injected command `<command>` is run in the user's shell without the user's permission.

This issue is occurring because when that menu entry is clicked, `jupyterlab-git` opens the terminal and runs `cd <git-repo-path>` through the shell to set the current directory [^3]. Doing so runs any command substitution strings present in the directory name, which leads to the command injection issue described here. A previous patch provided an incomplete fix [^4].

[^1]: https://www.gnu.org/software/bash/manual/html_node/Command-Substitution.html [^2]: https://www.gnu.org/software/libc/manual/html_node/File-Name-Portability.html [^3]: https://github.com/jupyterlab/jupyterlab-git/blob/7eb3b06f0092223bd5494688ec264527bbeb2195/src/commandsAndMenu.tsx#L175-L184 [^4]: https://github.com/jupyterlab/jupyterlab-git/pull/1196

## Scope of Impact

This issue allows for arbitrary code execution via command injection. A wide range of actions are permitted by this issue, including but not limited to: modifying files, exfiltrating data, halting services, or compromising the server's security rules.

We have scanned the source code of `jupyterlab-git` for other command injection risks, and have not found any at the time of writing.

This issue was reproduced on the latest release of `jupyterlab-git`, v0.51.0. The steps taken to reproduce this issue are described in the "Proof-of-concept" section below.

## Proof-of-concept

1. Create a new directory via `mkdir test/ && cd test/`.

2. Create a new Git repository under `test/` with a command substitution string in the directory name by running these commands:

``` mkdir '$(touch pwned.txt)' cd '$(touch pwned.txt)/' git init cd .. ```

3. Start JupyterLab from `test/` by running jupyter lab. 4. With JupyterLab open in the browser, double click on `$(touch pwned.txt)` in the file browser. 5. From the top menu bar, click "Git > Open Git Repository in Terminal". 6. Verify that `pwned.txt` is created under `test/`. This demonstrates the command injection issue described here.

## Proof-of-concept mitigation

The issue can be mitigated by the patch shown below.

<details><summary>Patch (click to expand)</summary>

```diff diff --git a/src/commandsAndMenu.tsx b/src/commandsAndMenu.tsx index 3779a6c..71ddcea 100644 --- a/src/commandsAndMenu.tsx +++ b/src/commandsAndMenu.tsx @@ -164,31 +164,13 @@ export function addCommands( label: trans.__('Open Git Repository in Terminal'), caption: trans.__('Open a New Terminal to the Git Repository'), execute: async args => { - const main = (await commands.execute( - 'terminal:create-new', - args - )) as MainAreaWidget<ITerminal.ITerminal>; + const cwd = gitModel.pathRepository; + const main = (await commands.execute('terminal:create-new', { + ...args, + cwd + })) as MainAreaWidget<ITerminal.ITerminal>; - try { - if (gitModel.pathRepository !== null) { - const terminal = main.content; - terminal.session.send({ - type: 'stdin', - content: [ - `cd "${gitModel.pathRepository - .split('"') - .join('\\"') - .split('`') - .join('\\`')}"\n` - ] - }); - } - - return main; - } catch (e) { - console.error(e); - main.dispose(); - } + return main; ``` </details>

This patch removes the `cd <git-repo-path>` shell command that causes the issue. To preserve the existing behavior, the `cwd` argument is set to `<git-repo-path>` when a terminal session is created via the `terminal:create-new` JupyterLab command. This preserves the existing application behavior while mitigating the command injection issue.

We have verified that this patch works when applied to a local installation of `jupyterlab-git`. We have also verified that the `cwd` argument is available in all versions of JupyterLab 4, so this patch should be fully backwards-compatible.

## Workarounds

We recommend that users upgrade to the patched versions listed on this GHSA. However, if a user is unable to upgrade, there are 3 different ways to mitigate this vulnerability without upgrading to a patch.

1. Disable terminals on `jupyter-server` level: ``` c.ServerApp.terminals_enabled = False ```

2. Disable the terminals server extension: ``` jupyter server extension disable jupyter_server_terminals ```

3. Disable the lab extension: ``` jupyter labextension disable @jupyterlab/terminal-extension ```