GitHub CLI vulnerable to Remote Code Execution through Malicious SSH Server

Summary

The GitHub CLI version 2.6.1 and earlier are vulnerable to remote code execution through a malicious codespace SSH server when using gh codespace ssh or gh codespace logs commands. This has been patched in the cli v2.62.0.

Developers connect to remote codespaces through an SSH server running within the devcontainer, which is generally provided through the [default devcontainer image]( https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/adding-a-dev-container-... https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/adding-a-dev-container-configuration/introduction-to-dev-containers#using-the-default-dev-container-configuration) . GitHub CLI [retrieves SSH connection details]( https://github.com/cli/cli/blob/30066b0042d0c5928d959e288144300cb28196c9/internal/codespaces/rpc/inv... https://github.com/cli/cli/blob/30066b0042d0c5928d959e288144300cb28196c9/internal/codespaces/rpc/invoker.go#L230-L244 ), such as remote username, which is used in [executing ssh commands]( https://github.com/cli/cli/blob/e356c69a6f0125cfaac782c35acf77314f18908d/pkg/cmd/codespace/ssh.go#L2... https://github.com/cli/cli/blob/e356c69a6f0125cfaac782c35acf77314f18908d/pkg/cmd/codespace/ssh.go#L263 ) for gh codespace ssh or gh codespace logs commands.

This exploit occurs when a malicious third-party devcontainer contains a modified SSH server that injects ssh arguments within the SSH connection details. gh codespace ssh and gh codespace logs commands could execute arbitrary code on the user's workstation if the remote username contains something like -oProxyCommand="echo hacked" #. The -oProxyCommand flag causes ssh to execute the provided command while # shell comment causes any other ssh arguments to be ignored.

In 2.62.0, the remote username information is being validated before being used.

Refferences